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MANUAL 


Military  Field  Engineering 


FOR  THE  USE  OF 


OFFICERS  AND  TROOPS  OF  THE  LINE. 

PREPARED  AT  THE 

UNITED  STATES  INFANTRY  AND  CAVAIvRY  SCHOOL 

BY  THE 

Department  of  Engineering, 

Capt.  Wm.  D.  Beach,  3d  Cavalry,  Instructor. 


SIXTH  EDITION 

REVISED  BY 

Major  Wm.  D.  Beach,  10th  Cavai^ry, 

Member  of  the  War  College  Board. 

Capt.  E.  a.  Root,  10th  Infantry.- 
Capt.  T.  H.  Si^avens.  Quartermaster,  U.  S.  A. 


The  Hddson-Kimberly  Publishing  Co., 
Kansas  City,  Mo. 


I.ONDON: 
W.  H.  AI,I,KN  &  CO.  (I^imited), 

13  Waterloo  Place,  S.  W. 
Publishers  to  the  India  Office. 


Entered  according  to  the  Act  of  Congress  in  the  year  1897,  by  the 

hudson-klmberly  publishing  cc,  in  the  office  of  the 

I^ibrarian  of  Congress,  at  Washington. 


Cop*YRi6HTEi5  1902,  ^y'the*  * 

HUDSON-KlM^ERiY  PC^M^ICSIING  C©MI»AK{Y, 


GIFT  OF 


PREFACE. 

The  necessity  existing  at  the  Infantry  and  Cavalry  School 
for  a  text-book  on  Field  Engineering,  including  the  various 
military  expedients  recognized  in  our  service,  is  deemed  suffi- 
cient reason  for  the  following  pages. 

Most  of  the  subjects  treated  of  in  this  volume  may  be  found 
in  various  military  works  published  in  our  country  during  the 
past  twenty-five  years,  but  the  fact  remains  that  no  one  book 
has  covered  the  required  ground,  nor  has  their  revision  been  of 
very  recent  date;  while,  at  the  same  time,  the  new  field  gun  and 
small  calibre  rifle  have  necessarily  modified  previously  exist- 
ing profiles  of  Field  Works  and  Shelter  Trenches. 

Access  has  been  had  to  corresponding  publications  of  the 
Germans,  French,  English  and  Austrians,  as  well  as  to  our 
own  Official  Rebellion  Records  and  many  other  available 
sources,  native  and  foreign. 

It  has  been  the  endeavor  to  limit  the  scope  of  this  work  to 
subjects  considered  indispensable  as  a  part  of  a  line  officer's 
education. 

•The  following  Assistant  Instructors  in  the  Department  of 
Engineering — viz.:  1st  Lieut.  E.  A.  Root,  19th  Infantry;  1st 
Lieut.  W.  C.  Wren,  17th  Infantry,  and  1st  Lieut.  T.  H.  Slavens, 
6th  Cavalry,  have  been  associated  with  the  undersigned  in  the 
preparation  of  this  volume. 

WM.  D.  BEACH, 
Captain,  3d  Cavalry, 
U.  S.  Infantry  and  Cavalry  School, 

Fort  Leavenworth,  Kansas,  July,  1894. 


921579 


Headquarters  of  the  Army,  Adjutant-Generars  Office, 

Washington,  March  25,  1895. 
Circular  No.  4. 

With  the  approval  of  the  Secretary  of  War,  the  special  study 
of  the  books,  pamphlets,  orders,  etc.,  hereinafter  named,  by 
officers  of  the  army  subject  to  examinations  for  promotion,  is 
recommended: 

Manual  of  Field  Engineering— Captain  W.  D.  Beach,  3pd 
Cavalry. 

By  command  of  Lieutenant-General  Schofield. 

[Signed]    GEO.  D.  RUGGLBS. 
AdJutant-OmeraL 


PREFACE  TO  THE  FIFTH  EDITION. 

A  fifth  edition  of  this  manual  having  been  called  for,  the  re- 
visers have  made  certain  alterations  and  additions  which  seem 
to  them  warranted  by  experiences  which  have  fallen  to  their  lot 
during  the  Spanish-American  War  and  Philippine  insurrection. 

The  peculiar  difficulties  confronting  a  rapidly  advancing  army 
are  such  as  to  render  familiarity  with  various  military  expedi- 
ents only  a  degree  less  important  than  an  intimate  acquaintance 
with  one's  weapon.  The  efficiency  of  a  command  may  be  para- 
lyzed by  the  lack  of  a  practicable  road  or  by  reason  of  a  broken 
bridge  as  effectually  as  by  tactical  blunders  or  failure  to 
reconnoiter. 

Hasty  intrenchments  are  more  than  ever  important,  and  there 
seems  little  reason  to  doubt,  judging  from  our  experience  before 
El  Caney  and  at  San  Juan  Hill,  that  odds  of  ten  to  one  will  here- 
after be  necessary  in  order  to  successfully  assault  trenches  de- 
fended by  good  infantry  armed  with  a  magazine  rifle.  This  de- 
duction was  originally  made  by  Colonel  A.  L.  Wagner,  A.  A.-G.,  in 
a  report  on  El  Caney,  and  is  borne  out  by  a  critical  study  of  the 
fight  at  San  Juan  Hill  and  various  actions  during  the  Boer  War 
in  South  Africa. 

Recent  experiences  but  render  more  certain  the  assertion  that 
the  assailant  will  usually  find  it  necessary  to  intrench,  the  de- 
fender always. 

Upon  the  line  officer  in  the  future  as  in  the  past  will  devolve 
the  responsibility  of  tracing  and  directing  the  construction  of 
shelter  trenches  as  well  as  making  intelligent  use  of  expedients 
in  bridging,  rafting,  road-building  or  camping. 

As  modern  civilization  tends  to  diminish  the  number  of  men 
skilled  in  handicraft,  so  much  the  more  important  does  it  become 
that  all  officers  should  require  greater  familiarity  with  what 
are  ordinarily  termed  ''military  expedients."  Results  may  be 
reached  in  many  ways,  but  their  attainment  with  economy  of  life 
and  treasure  marks  a  soldier  skilled  in  his  art,  a  leader  worthy 
the  best  traditions  of  the  military  service. 

W.  D.  B 

Fort  Leavenworth,  Kansas,  August,  1902. 


List  of  Books  Consulted  in  the  Preparation  of  this  Work. 

Aide  Memoire,  R.  E Vols,  j-2, 

A  Move  for  Better  Roads L,  A.  Haupi, 

Appleton's  Cyclopaedia  of  Applied  Mechanics,  Vols,  1-2, 

Civil  Engineering Wheeler, 

Cours  de  Fortification  Passagere De  Guise, 

Ecole  de  Fortification  de  Campagne French, 

Elements  of  Field  Fortification Wheeler, 

Engineering  News Magazine, 

Engineer's  Pocket-Book Trautwine, 

Field  Fortification Turner. 

Field  Fortification Hutchinson, 

Field  Works Brackenbury^ 

Field  Works  Used  in  War,     (Translation 

from  the  German)  Wilson, 

Good  Roads Magazine, 

Gun  Powder  and  High  Explosives Walke, 

International  Cyclopaedia Dodd,  Mead  &  Co* 

Journal  of  the  Military  Service  Institution 

of  the  U.  S. 
Journal  of  the  U.  S.  Cavalry  Association, 

Manual  for  Engineer  Troops Duane, 

Manual  of  Military  Engineering Ernst, 

Manual  for  Railway  Engineers G,  L,  Vose, 

Manuel  de  Fortification  de  Campagne. . . .  Brialmont, 
Manuel   des   Travaux  de  Fortification    de 

Campagne,  par  un  Capitaine  d'Infanterie. 

Manuel  de  Fortification Plessix  and  Legrand, 

Manual  of  Heavy  Artillery Tidball, 

Military  Bridges Haupt, 

Military  Bridges. Chester. 

Military  Engineering,  Instruction  in Chatham  Course, 

Military  Land  Mines Mercur. 

Military  Transport Furse, 

Modern  High  Explosives Eissler, 

Notes  on  Military  Hygiene A.  A.  Woodhull, 

Official  Records  of  the  Rebellion,  U.  S .  . .  .  War  Department, 

Organization  and  Tactics Wagner,      * 

Pionier  Taschenbuch,  Berlin,  1893 Official, 

Report  of  Chief  Signal  Officer,  U.  S.,  1893. .  War  Department, 

Roads  and  Railroads Chester. 

Roads  and  Railroads Gillespie* 

Roads,  Stieets,  and  Pavements Gitlmore, 

Temporary  Fortification Chester. 

The  American  Railway Scribner, 

U.  S.  Bridge  Equipage  and  Drill  . . , , War  Department 


TABLE  OF  CONTENTS. 

Chapter.  Page. 

I.  General  Principles 7 

II.  Fire,  Projectiles  and  Penetration 11 

III.  Field  Geometry 15 

IV.  Hasty  Intrenchments,  Gun  Pits  and  Epaule- 

ments 21 

V.  Clearing  the  Ground 28 

VI.  Obstacles 32 

VII.  Field  Works 39 

VIII.  Working  Parties 57 

IX.  Revetting  Materials  and  Revetments 61 

X.  Field  Casemates  and  Magazines .-.  73 

XI.  Field  Works  in  Combination 78 

XII.  Siege  Works 84 

XIII.  Defense  of  Localities 88 

XIV.  Use  of  Cordage  and  Spars 105 

XV.  Spar  Bridges 118 

XVI.  Floating  Bridges 140 

XVII.  Roads 168 

XVIII.  Railroads 175 

XIX.  Telegraph  and  Telephone  Lines 186 

XX.  Demolitions 191 

XXI.  Camping  Expedients 205 


Plate. 


1,  2 

3,  4 

5,  6 

7,  8 

9-15 

16 

17,  18 

19,  20 

21 

22,  23 

24-29 

30-33 

34-40a 

41-49 

50 

51-53 

54 

55-57 

58-60 


WLA.lSlxy^s.1^ 


OF 


MILITARY  FIELD  ENGINEERING 


CHAPTER  I.— General  Principles. 

1.— Military  Field  Engineering  may  be  defined  to  be  the  art 
of  utilizing  the  materials  at  hand  for  the  attainment  of  the  secu- 
rity, effectiveness,  health  and  comfort  of  an  army  in  the  field. 

The  modern  rifle  has  vastly  increased  the  value  of  cover,  both 
iu  attack  and  defense,  and  rendered  necessary  the  application  of 
ihe  principles  of  fortification  to  an  army  in  the  field.  The  result 
to  be  obtained  in  all  fortification  is  to  so  strengthen  a  position,  by 
artificial  means,  that  a  force  occupying  it  may  successfully  resist 
or  subdue  another  attacking  it. 

2.— Fortification  is  divided  into  two  general  classes,  viz.: 

(^(7j— Permanent. 

^&;— Temporary  or  Field  Fortifications. 

With  the  former  this  manual  has  nothing  to  do. 

3.— The  latter  division  includes  three  quite  distinct  classes. 

The  first  comprises  all  works  devised  for  the  temporary  protec- 
tion of  important  points,  such  as  cities,  arsenals,  bridges,  fords, 
positions,  etc.,  and  are  techuicallv  known  as  Field  Works. 

7 


9 ,  *  (?e»^<3ti  Principle*. 


''1?Iie*sec\)rfd  c6in]prt1^es"the  various  devices  of  the  engineer  for 
reducing  a  fortified  place  by  means  of  parallels  and  approaches, 
called  Siepe  Works. 

The  third  division  relates  particularly  to  the  quickly  made 
defenses  by  which  an  army  in  the  presence  of  an  enemy  protects 
itself;  these  are  known  as  Battle  Intrenchments  or  Hasty  Intrench- 
merits, 

4.— A  Defensive  Position  is  one  affording  protection  from 
the  shot  and  observation  of  an  enemy  and,  at  the  same  time,  com- 
manding the  ground  in  front,  within  range. 

A  position  of  perfect  defense  is  not  possible,  but  the  following 
general  principles  are  to  be  fulfilled  as  nearly  as  circumstances 
will  permit. 

(1)  The  defenders'  position  should  conform  to  the  special  tacti- 
cal requirements  of  the  occasion*  and  should  be  such  as  to  favor 
the  use  of  their  relatively,  strongest  arm. 

(2)  It  should  be  made  impossible  for  the  enemy  to  obtain  nat- 
ural cover  during  his  advance.  In  other  words,  the  position  should 
have  a  free  field  of  fire. 

(3)  The  defenders  should  be  protected  from  the  fire  and  view  of 
the  enemy  by  cover  so  arranged  as  not  to  interfere  with  counter- 
attacks. 

(4)  The  advance  of  the  enemy  should  be  hindered  by  obstacles 
so  arranged  that  he  may  be  checked  while  under  the  fire  of  the 
defenders. 

(5)  Communications  should  be  such  that  the  defenders  may 
freely  move  from  one  part  o^  the  position  to  another,  while  the 
contrary  should  obtain  witb  respect  to  the  enemy's  ground  in 
front. 

The  chief  requisite  of  a  defensive  position  is  a  free  field  of  fire, 
especially  at  short  and  mid  ranges.  If  the  position  is  judiciously 
selected  the  field  of  fire  will  generally  be  obtained  without  much 
difficulty,  but  the  advantages  of  the  position  and  the  effect  of  the 
fire  may  be  enhanced  by  temporary  fortifications.  The  cutting 
down  of  slight  ridges  which  might  afford  cover  for  th^e  enemj 


♦A.  r>ure1v  defensive  nosition .  for  instan^'e,  mig-ht  have  its  flanks  resting-  on  im- 
passfible  obstacles,  and  thns  be  secure  from  a  turning  movement,  but  this  same 
position  ♦^ig'ht  be  found  to  be  a  faulty  one  were  a  quick  offensive  movement,  by 
the  defenders,  contemplated. 


General  Principles,  ^  9 

within  effective  range  or  the  removal  of  hedges,  fences,  etc.,  may 
sometimes  be  of  more  benefit  than  the  actual  preparation  of 
defenses. 

In  the  present  advanced  state  of  efficiency  of  fire-arms,  artificial 
cover  is,  however,  of  greater  importance  than  ever  before.  Con- 
structed in  the  right  place,  at  the  proper  time,  field  fortifications 
may  render  indispensable  service,  while  their  neglect  may  insure 
defeat. 

5.— While  formerly  it  was  the  special  province  of  the  Engineer 
to  lay  out  and  supervise  the  construction  of  defensive  works,  it 
has  now,  under  the  changed  condition  of  warfare,  become  the  work 
of  the  Line  as  well,  and  it  may  be  laid  down  as  an  accepted  rule 
that  the  defensive  arrangements  for  a  given  position  are  to  be 
made  by  the  troops  which  are  to  occupy  it. 

These  changes  have  affected  the  art  in  many  ways.  The  field 
works  now  constructed  are  simpler,  ruder,  less  regular,  and  less 
angular  than  before.  An  army  in  the  presence  of  an  enemy  always 
fortifies,  whether  in  camp,  in  bivouac,  or  in  line. 

6.— Rapidity  of  execution  renders  necessary  the  adoption  of 
fixed  types  of  works  in  the  exercises  in  time  of  peace;  but  these 
types  will  sometimes  be  susceptible  of  modification  in  their  real 
application.  However,  even  in  war,  the  endeavor  should  be  to 
approximate  to  the  regulation  forms,  for  they  are  deduced  from 
experience  and  observation,  and  realize,  as  well  as  possible,  for 
each  particular  case,  the  best  conditions  of  resistance  compatible 
with  rapidity  of  execution. 

The  advantage  of  regulation  types  is  understood  at  once  when 
it  is  borne  in  mind  that,  upon  the  battle-field,  there  should  be  no 
hesitation;  everyone  should  stick  to  his  individual  role  in  order 
to  unite  efficiently  in  combined  action. 

Thorough  study  and  frequent  practical  exercises,  conducted 
methodically,  are  indispensable  In  order  to  escape  feeling  one's 
way,  with  the  loss  of  time  that  an  insufficient  instruction  renders 
inevitable.  Upon  the  battle-field  a  few  minutes  may  decide  the 
fate  of  armies  in  each  other's  sight. 

7.— Fortification,  which  at  first  glance  may  appear  to  dominate, 
as  representing  the  "security"  and  * 'effectiveness"  of  an  army. 


10  General  Principles. 

the  other  and  apparently  less  important  subjects  relating  to  health 
and  comfort,  is,  however,  so  intimately  connected  with  them  that 
neglect  of  one  may  render  all  the  others  useless.  Thus,  ^'bridges," 
"roads,"  and  "railroads"  may,  under  certain  conditions,  relate  par- 
ticularly to  the  effectiveness  and  security  of  an  army,  in  con- 
nection with  Fortification,  while  under  other  circumstances  they 
may  be  as  important  as  various  "camping  expedients"  in  the 
attainment  of  "health"  and  "comfort." 


CHAPTER  II.— Fire,  Projectiles  and  Penetration. 

8.— Pire  as  regards  its  direction  is  classified  as  follows: 

(1)  Prontal,  when  it  is  delivered  at  right  angles  to  tlie  front 
of  the  enemy's  line,  and  sometimes  so  termed  when  delivered 
straight  to  its  own  front. 

(2)  Oblique,  when  the  direction  of  the  fire  is  at  an  oblique  angle 
to  the  front  of  the  enemy's  line. 

(3)  Enfilade,  which  is  delivered  from  positions  on  the  prolon- 
gation of  the  enemy's  line.  In  this  case,  the  line  of  fire  sweeps 
the  enemy's  front.  When  fire  is  used  to  sweep  along  the  front  of 
a  defensive  line  and  thus  enfilade  the  assailants  as  they  approach 
the  position,  it  is  known  as  flanking  fire. 

(4)  Reverse,  when  delivered  so  as  to  strike  troops  or  lines  oj 
defense  from  the  rear. 

(5)  Cross,  when  the  lines  of  fire  from  different  positions  cross 
on  or  in  front  of  the  enemy's  line. 

As  regards  its  trajectory  it  is  classified  as 

(1)  Direct,  when  delivered  at  seen  objects  at  moderate  angles 
of  elevation— in  the  case  of  artillery  when  delivered  at  seen  objects, 
with  service  charges  at  elevations  not  exceeding  15". 

(2)  Indirect  or  Curved,  when  delivered  with  small-arms  against 
an  unseen  object  protected  by  a  seen  covering  obstacle— in  the  case 
of  artillery,  as  above,  or  with  guns,  howitzers  or  mortars  with 
reduced  charges  at  angles  not  exceeding  15°.  Thus  firing  over  an 
intervening  hill  at  troops  sheltered  behind  it  would  be  an  example 
of  indirect  fire. 

(3)  High  Angle,  when  used  at  angles  exceeding  15**. 

(4)  Grazing,  when  the  projectile  travels  approximately  parallel 
to  the  ground. 

(5)  Plunging,  the  muzzle  is  required  to  be  depressed. 

9.— The  Artillery  Projectiles  used  in  the  U.  S.  Army  are  sJiell, 
shrapnel  and  canister. 


12  Fire,  trojtctiU^  and  Penetration. 

i&neii.— toiieii  may  be  classiiieu  as  commou  sliell  aud  torpeuo 
jsiiell.  Tlie  commou  sliell  is  "a  noliovv  cast-irou  or  steel  eylmder 
with  au  ogival  Head  closed  ai  oue  end  and  niled  witn  powder." 
Tlie  torpedo  sliell  is  Ulled  witii  gun-cottou,  or  otiier  liigli  explo- 
sive. Either  shell  may  be  ciiaracterized  as  a  llyiug  mine,  the 
chief  object  of  which  is  to  destroy  material  objects  at  a  distance, 
though  the  commou  shell  may  also  be  effectively  used  against 
troops. 

10.— Shrapnel  differs  from  common  shell  in  being  filled  with 
bullets,  and  having  only  a  sufficient  bursting  charge  to  rupture 
the  envelope  and  release  the  bullets,  which  then  move  with  a  veloc- 
ity which  the  projectile  had  at  the  moment  of  bursting.  The  bul- 
lets are  assembled  in  circular  layers  and  held  in  position  by  "sep- 
arators," which  are  short  cast-iron  cylinders  with  hemispherical 
cavities  into  which  the  bullets  fit.  The  shrapnel  for  the  3.2  inch 
gun  contain  1G2  bullets  i^  in.  in  diameter,  and  weighing  41  to  the 
lb.  The  total  number  of  bullets  and  individual  pieces  in  the  shrap- 
nel is  201  when  assembled,  and  many  more  after  bursting. 

11.— Canister,  which  is  practically  obsolete,  is  made  of  sheet- 
iron  or  tin  in  the  shape  of  an  ordinary  can,  and  is  filled  with  bul- 
lets held  in  place  by  filling  the  interstices  between  the  bullets  with 
saw-dust,  sulphur  or  rosin;  the  can  is  ruptured  and  its  contents 
dispersed  by  the  discharge  of  the  piece. 

12.— The  charges  in  the  shell  and  shrapnel  are  exploded  by 
means  of  a  combination  fuse;  by  combination  fuse  is  meant  one 
that  may  be  arranged  to  explode  the  charge  either  on  impact,  by 
percussion,  or  at  a  given  time  by  certain  arrangement  of  the  parts 
of  the  fuse. 

13.— Field  Guns  range  up  to  6000  yds.,  but  will  be  seldom  usea 
at  a  range  greater  than  2500  yds. 

14.— The  XJ.  S.  Magazine  Bifle,  when  used  as  a  single  loader, 
has  fired  21  aimed  shots  in  one  minute,  and  when  used  as  a  maga- 
zine rifie,  23  shots  in  one  minute;  its  range  is  over  3000  yds.  and  it 
is  sighted  to  1900  yds. 

The  average  heights  over  which  fire  may  be  delivered  are  as 
follows:  Man  standing,  4  ft.  4  in.;  kneeling,  3  ft.;  lying  down,  1  ft.; 
field  guns,  3  ft 


I^irt,  rrojtvH(A^  and  Penetration.  id 

iu.— Xiie  lolluvviii^  Luicivuefcjs  ol  maLeiial  may  be  couisiaered  ab 
jji'ool:  agaiust  small-arm  projectiles  at  all  ranges: 

;baud 30  in. 

Jiiartn 3y  in. 

i:>os8y  or  ini'Ly  oxuaiiu 60  in. 

ijiabiou  niled  wuu  eartn 1 

Well-made  fascines '6 

fciaud  bag  well  packed,  neaaer 1 

**  stretcjLier 2 

stacked  sod 79  in. 

Packed  snow 79  in. 

Soit  wood 40  to  49  in. 

Oak  or  other  bard  wood 24  in. 

Grain  sheaves  piled 16  ft. 

Iron  plate 7-16  in. 

Steel  plate %  in. 

♦Masonry  brickwork  with  broken  joints 20  in. 

Crib  of  broken  stone 8  in. 

Against  field  artillery. 

Sand 10  ft. 

Earth 13  ft 

Clay 17  ft. 

Snow  well  packed 27  ft. 

Masonry  (for  a  short  time; 40  in. 

*A  wall  two  bricks  thick,  breaking  the  joints,  will  stop  any  one 
bullet,  but  after  a  time  the  bricks  will  ibe  smashed  and  some  bul- 
lets get  through. 

A  well-built  wall  with  fine  joints  set  in  cement  mortar,  9  inches 
thick,  is  practically  bullet-proof. 

A  24 -inch  sun-dried  brick  wall  is  fairly  bullet-proof  a  short 
time  after  setting. 

15a. — ^The  mean  penetration  of  shells  from  siege  gims,  with  a 
striking  velocity  of  about  800  feet,  is: 

6-inch    8-  and  10-inch 
Guns.  Guns. 

Feet.  Feet. 

Sand,  mixed  with  gravel 9.84  11.48 

Light  earth 13.12  16.73 

Light  earth,  loose  (newly  stirred  up) 14.76  20.34 

Clay  (argillaceous  earth) 21.33  27.89 


14  Fire,  Projectiles  and  Penetration. 

Dlmeoasions  of  craters  made  by  6-  and  8.5-iiicli  shells: 

6-lnch.  8.5-inch. 

Diam.        Depth.        Diain.         Depth. 
Feet.  Feet.         Feet.  Feet. 

Clayey  earth 16.48  4.9  22.3  6.9 

Calcareous  sandstone 13.1  3.3         16.4  3.9 

Concrete 9.8  3  11.5  3.3 

Rough  masonry 9  2  6.6  3 

Note, — ^With  delayed-action  fuses,  shells  burst  after  gaining  a 
certain  penetration.  The  maximum  effect  of  the  bursting  charge 
will  be  found  on  the  line  of  least  resistance. 


CHAPTER  III.— Field  Geometry. 


16.— Before  proceeding  to  that  portion  of  field  engineering 
which  involves  geometry  some  of  its  simplest  applications  will  be 
explained. 

17. — Slopes.  Tlie  usual  description  of  a  slope  is  by  a  fraction, 
the  numerator  being  the  height  and  the  denominator  the  base. 
Thus,  in  PL  1,  Fig.  1,  the  vertical  height  is  l-6th  part  of  the  base, 
and  the  slope  is  read  as  1  on  6.    In  Fig.  2,  the  slope  is  6  on  1. 

18.— To  lay  out  a  Right  Angle:  First  Method.  Let  A  be  a 
point  in  the  line  BC,  Fig.  3.  Lay  off  from  A  the  equal  distances 
AD  and  AE.  With  a  radius  greater  than  AD,  and  with  D  and  E 
as  centers,  describe  arcs  cutting  each  other  at  X.  Join  X  with  A. 
Then  is  XA  perpendicular  to  BC. 

Second  Method.  Find  a  point  such  that  the  distances  are  in  the 
proportions  of  3,  4  and  5:  then  will  the  angle  included  between  the 
two  shorter  sides  be  a  right  angle  Thus  (Fig.  4)  with  chain  or 
tape  measure  the  distance  AD  equal  to  4  yds.  Place  one  end  of 
tape  at  D,  the  other  at  A,  pulling  it  out  and  making  XD  equal  to  5 
yds.,  XA  equal  to  3  yds. 

Third  Method.  At  extremity  of  line,  as  A  (Fig.  4),  assume  any 
))oint  as  C.  Measure  distance  CA,  set  a  stake  on  line  BA  at  a  dis- 
tance from  C  equal  to  CA,  as  D.  Set  a  third  stake  on  line  CD  at  X, 
making  CX  equal  to  CD.  Then  will  XA  be  perpendicular  to 
BA. 

19. — To  erect  a  perpendicular  to  a  line  from,  a  point  without. 
Ivet  X  (Fig.  5)  be  the  point  without,  then,  with  X  as  a  center,  and 
a  distance  greater  than  XA  as  radius,  describe  an  arc  cutting  BC 
at  D  and  E.  With  D  and  E  as  centers,  and  with  a  radius  greater 
than  DA,  describe  arcs  cutting  each  other  at  Y.  Join  X  and  Y. 
Then  will  XY  be  perpendicular  to  BC. 

20.— -To  bisect  a  given  angle.  Let  BAG  (Fig.  6)  be  the  angle. 
With  A  as  a  center,  and  with  any  convenient  radius,  as  AD, 
—2- 


PLATE  1. 


•Figure  1. 


Figure  2. 


Figure  3. 


B     '.D 

Figure  4 


/E    c 

X 


cK 


Figure  5  . 


Figure  6. 


Figure  7y 


A  *     c     ' 


Figure  10. 


D     '    B 


B       D" 


E     C 


B       0    C 


Figure  11 


.X 

Y 


Field  Geometry.  17 

aescribe  an  aic  cutting  AB  and  AG  at  E  and  D.  With  D  and  E  as 
centers,  describe  arcs  cutting  eacli  otlier  at  X.  Join  X  with  A. 
The  liue  XA  bisects  the  angle  BAG. 

21. — To  lay  out  an  equilateral  triangle  constructing  adjacent 
angles  of  60 ""  and  120"^.  Let  AB  (Fig.  7)  be  a  given  line.  Lay 
off  from  B  any  convenient  distance,  as  BE.  Then,  with  B  and  E 
as  centers,  and  a  radius  equal  to  BE,  describe  arcs  cutting  each 
other  at  D.  Join  D  with  E  and  B.  The  angles  DEB,  DBE  and 
EDB  are  each  equal  to  60°.  The  angle  AED  is  equal  to  120°. 
Combining  this  method  with  that  of  slopes  an  angle  of  almost  any 
number  of  degrees  can  be  laid  out. 

22. — To  lay  out  an  angle  equal  to  a  given  angle.  Let  X 
(Fig.  8)  be  a  point  in  the  line  AB,  from  which  it  is  required  to  lay 
out  an  angle  equal  to  OEG.  Fix  the  points  O  and  G  at  convenient 
distances  from  E.  From  X  lay  off  Xg  equal  to  OE.  Then,  with 
X  and  G  as  centers,  and  EG  and  OG  as  radii  respectively,  strike 
arcs  intersecting  at  F.  Join  X  and  F.  The  angle  FXG  is  equal  to 
the  angle  GEO. 

23. — To  draw  a  line  parallel  to  a  given  line  and  at  a  given 
distance  from  it.  Let  AB  (Fig.  9)  be  the  given  line.  From  any 
two  points,  as  G  and  D,  erect  perpendiculars.  On  these  lay  off  the 
required  distance  CE  and  DF.    Join  E  and  F. 

24. — To  find  the  distance  between  any  two  points  when  it 
cannot  be  measured  directly.  First  Method.  To  find  AO,  take 
a  point  B  in  line  with  AO  and  from  this  point  (Fig.  10)  lay  off  any 
convenient  angle,  as  ABG.  At  D  make  EDG  equal  to  ABG.  Meas- 
ure BG,  DG  and  DE,  putting  E  in  the  line  GO.  From  similar 
triangles 

BO  X  DE 

BO  :  BG  ::  DE  :  DG  ;•.  BO  = 

DG 

From  the  result  thus  found,  subtract  the  distance  AB.  The 
remainder  is  the  distance  AO. 

Second  Method.  (Fig.  11.)  Mark  B  in  prolongation  of  the  line 
AO.  Assume  any  point  as  G.  Lay  off  AF,  making  AG  equal  to 
GP:  also  BE,  making  BG  equal  to  GE.  Prolong  EF  until  a  point 
K  is  found  in  line  with  GO.  Measure  FK.  This  is  the  required 
distance. 


18  Field  Oeometry, 

25. — ^Areas.  To  find  the  area  of  a  rectangle.  Multiply  the 
base  by  the  height 

To  find  the  area  of  a  trapezoid.  Multiply  the  sum  of  the  two 
parallel  sides  by  the  perpendicular  distance  between  them  and 
take  half  the  product. 

To  find  the  area  of  a  triangle.  Multiply  the  base  by  the  alti- 
tude and  take  half  the  product.    Or, 

Area  =    V  s  (s  — a)  (s  —  b)  (s  — c) 
in  which  s  is  the  half  sum  of  the  three  sides  a,  b,  and  c.    Or, 

Area  =  %  a  b  sin  O 
in  which  a  and  b  are  two  sides  and  C  the  included  angle. 

26.— The  Field  Level  (PI.  2,  Fig.  1)  consists  of  three  strips  of 
wood,  A,  B  and  C,  each  ^  in.  thick  and  2  in.  wide.  A  being  62  in. 
long,  B  and  C  each  44.42  in.  The  distance  between  centers  on  A  is 
60  in.,  on  B  and  C  42.42  in.  This  makes  a  right  angle  between  B 
and  C.  There  is  a  thumb  nut  at  E  clamping  the  arm  B  to  the  arm 
A  when  the  level  is  used.  The  screw  at  F  projects,  holding  the 
arm  B,  when  folded,  up.  There  is  a  stud  at  H,  affording  an  attach- 
ment for  a  plumb  bob.  There  are  permanent  joints  between  B 
and  C,  and  A  and  C. 

Fig.  1  shows  the  level  and  its  joints,  plumb  bob  for  reading 
slopes,  and  spirit  level.    Fig.  2  shows  side  for  protracting  angles. 

27. — Uses  of  Level.    The  level  may  be  used  as  follows: 

(1)  As  a  spirit-level,  the  level  being  on  the  edge  C. 

(2)  As  a  square  for  setting  out  a  right  angle. 

(3)  As  a  protractor. 

(4)  For  setting  off  slopes. 

(5)  As  a  mason's  level  with  a  plumb  bob. 


PLATE  2. 


PLATE  3. 


SHELTER  TRENCH. 

-  LYING- 


FiG.4. 


SPLINTER    PROOF, 

(earth     cover     omitted). 


Fig.  5.     SHELTER  rof^  SUPPORTS  oh  RESERVES. 


HEAD    LOG   AND 
BRUSH-WOOD      LOOPHOLE, 


LOOP-HOLE 


!rfl6i«97 


CHAPTER   IV.— Hasty   Intrenchments,   Gun  Pits   and 
Epaulements. 

28. — The  intensity  of  fire  made  possible  by  the  fire-arms  of 
to-day  renders  some  form  of  shelter  on  the  field  of  battle  impera- 
tive. Circumstances  may  occur  when  advancing  lines  of  skirmish- 
ers will  find  natural  shelter,  but  in  many  cases  artificial  cover  will 
have  to  be  constructed  on  the  spot. 

Fortifications  used  on  the  field  of  battle  depend,  as  to  their  posi- 
tion, extent  and  use,  on  the  ground;  in  conformity  to  this  idea 
they  are  constructed  at  the  time  of  the  battle,  and  not  before. 

They  are  called  *' Battle"  or  ^^East<y'^  Intrenchments,  and  should 
fulfill  the  following  conditions: 

(a)  The  thickness  of  earth  embankment  should  be  such  that  it 
will  not  be  liable  to  penetration  by  small-arm  projectiles  or  shrap- 
nel fragments.  %^ 

(h)  The  intrenchments  should  conform  to  the  average  heights 
over  which  men  can  fire  in  the  various  positions,— viz. :  lying  prone, 
1  ft.;  kneeling,  3  ft:  standing,  4  ft.  4  in.;  and  at  the  same  time  the 
height  of  earth  embankment  above  the  natural  surface  of  the 
ground  should  be  small,  for  the  reason  that  the  trenches  can  thus 
be  more  easily  concealed  and  are  less  liable  to  be  struck  by  artil- 
lery projectiles. 

Hasty  or  Battle  Intrenchments  consist  of  cover  for 

(1)  Skirmishers,  lying,  kneeling  or  sitting. 

(2)  Firing  Line,  Supports  and  Reserves,  kneeling,  sitting  or 
standing. 

(3)  Gun  Pits  and  Epaulements. 

r59. — The  shelter  trench  for  skirmishers  lying  down  is  shown 
in  Fl.  3,  Fig.  1.  It  gives  earth  protection  of  a  thickness  of  2^  feet; 
this  thickness  of  loose  earth  will  stop  small-arm  projectiles  under 
ordinary  circumstances.  The  average  time  required  by  one  man 
to  make  5  ft.  (2  paces)  of  this  trench  is,  with  large  pick  and  shovel, 
15  minutes;  with  small  intrenching  spade,  20  to  25  minutes. 

The  number  of  skirmishers  that  can  use  this  trench  is  usually 
computed  as  two  for  each  five  feet  of  length,  although  three. may 
occupy  this  space  by  lying  partially  on  their  left  sides.  In  firing, 
the  left  elbow  rests  on  the  berm. 

30. — For  men  kneeling  in  two  ranks,  cover  is  gained  by  deep 
ening  the  trench  already  dug  to  1  ft.  8  In.  and  making  it  5  ft.  wide 


22      Hasty  Intrenchments,  Chin  Pits  and  Epaulements. 

with  an  embankment  in  front  having  a  height  of  1  ft.  4  in.  and  a 
resulting  thicliness  of  about  ^Vo  ft.      (Fig.  2.) 

The  average  time  required  by  one  man  to  transform  5  ft.  of  the 
trench  ''lying"  into  the  trench  "lineeling"  is,  with  large  pick  and 
shovel,  25  minutes;  with  small  intrenching  spade,  45  minutes. 

Infantry  in  double  rank  kneeling  can  fire  from  this  trench,  the 
number  of  rifles  being  computed  at  4  for  each  5  ft.  length  of  trench. 
The  kneeling  trench  affords  protection  to  men  sitting,  but  hori-  ^ 
zontal  fire  from  this  position  is  impossible.     The  step  at  a  would 
only  appear  in  the  converted  trench. 

31. — Cover  standing  is  obtained  by  deepening  the  kneeling 
trench  to  4  ft,  leaving  a  step  20  in.  high  and  3  ft.  wide  next 
the  front  wall,  so  as  to  facilitate  leaving  the  trench  to  the 
front  and  at  the  same  time  allowing  a  protected  passage  in 
rear.  The  step  serves  as  a  banquette  for  men  firing  over  the 
embankment. 

The  embankment  is  given  a  height  of  2  ft.,  the  resulting  thick- 
ness being  about  5^  ft.    (Fig.  3.) 

The  average  time  required  by  one  man  to  transform  5  ft.  of 
the  trench  "kneeling"  into  the  trench  "standing"  is,  with  large 
pick  and  shovel,  1  hour.* 

32. — When  isolated  trenches  for  single  skii^misliers  lying  are 
desired,  they  should  be  made  with  the  same  section  as  that  shown 
in  Figure  1  and  have  a  length  of  1  pace.  Isolated  kneeling  trenches 
for  two  men  should  also  have  a  length  of  1  pace,  but  the 
rifle  pit  or  isolated  slielter  standina  should  be  5  ft.  in  length  on 
account  of  difficulty  in  constructing  a  smaller  one.  The  last  read- 
ily accommodates  three  men,  two  of  whom  can  fire  over  the 
embankment,  while  the  third,  standing  in  the  4  ft.  trench,  pro- 
tects the  flanks. 

33. — When  necessary  to  intrench  supports  and  reserves,  the  cover 


-The  orditiRry  form  of  ^Danish  hastv  intrenchment  for  fire,  standing  and  cover 
sitting:,  kneeling- or  crouching  is  a  trench  abont  two  feet  wide  and  four  feet  deet), 
having  vertical  sides  and  no  embankments.  This  type  of  trench  does  not  readilv 
permit  relieving  or  re  inforcing  the  occupants  an'^.  as  it  is  too  narrow  to  permit 
rarrving  the  wounded  out.  there  re.«n1ts  extreme  snfFerine.  since  the  injured  mu.st 
lie  at  the  bottom  and  run  th^  risk  of  being  trampled  upon.  This  trench  has  the 
advantage  however  of  affording  a  .email  target  for  the  enemy's  artillery. 

The  f^ermans  claim  that  the  surface  presented  to  .<;hrapnel  bullets  by  a  man 
Iving  down  is  nracticallv  the  .<5ame  as  a  man  standing  in  the  open:  therefore  they 
do  not  believe  in  broad  s"Hallow  trenche.s.  Thev  advocate  the  making  of  trenches 
in  the  natural  soil  with  the  fresh  earth  carried  away,  or  used  fo-  dummy  trenches 
so  as  to  deceive  the  enemy's  artillerists  and  prevent  execution  from  shrapnel  fire. 


Hasty  Intrenchments,  Gun  Pits  cmd  Epaulements.     23 

kneeling  or  standing  should  be  used  in  parallel  rows  close  to  one 
another.    (Fig.  5.) 

In  the  construction  advantage  should  be  taken,  where  possible, 
of  plows  for  loosening  the  earth.  Two  or  three  plows  following 
each  other  at  intervals  can  be  used  to  great  advantage. 

34. — The  trenches  here  illustrated  are  all  made  on  level 
ground  and  are  simply  Ujpes  showing  the  best  forms  and  giving 
general  ideas  as  to  the  time  required  to  construct  cover.*  On 
slopes  they  must  be  modified  so  that  the  tops  of  tlie  embank- 
ments are,  in  general,  parallel  to  the  ground;  they  may  also  be 
varied  according  to  the  kind  of  earth,  sand  requiring  less  thick- 
ness of  embankment  and  gentler  slopes  than  clayey  soil,  while 
sod  mixed  with  earth  allows  greater  penetration  than  earth 
without  it. 

35. — The  location  of  trenches  depends  primarily  on  tactical 
situations,  and  secondarily  on  the  nature  of  the  ground. 

Primarily,  they  should  always  occupy  a  position  giving  the 
greatest  development  of  fire,  and  hence  are  generally  located 
near  tJie  crest  of  the  most  ahrupt  slope— i.  e.,  near  the  *'mAlitary 
cresty  (See  par.  153.)  Tlie  exact  position  is  determined  "by  plan- 
ing the  eye  at  a  distance  above  the  ground  equal  to  the  proposed  height 
of  embankment,  and  then  selecting  that  line  which  gives  a  clear  field  of 
fire  to  the  front. 

As  to  the  secondary  consideration,  it  is  desirable  in  locating 
trenches  to  avoid  stony  ground  and  that  close  to  the  edges  of 
woods,  the  former  on  account  of  the  liability  to  flying  frag- 
ments should  the  embankment  be  struck  by  an  artillery  projectile, 
and  the  latter  by  reason  of  the  difficulty  in  constructing  the 
trenches. 

36. — ^Intervals  in  line  of  trenches.  In  all  trenches  except 
those  for  skirmishers  lying  down,  intervals  in  the  line  should  be 
left  for  the  passage  to  the  front  of  artillery  and  cavalry— this 
is  especially  necessary  when  cover  standing  is  used.  The  inter- 
vals may  vary  in  width  according  to  circumstances,  but  should 
never  be  so  wide  as  to  preclude  their  defense  by  the  trenches 
adjoining  the  opening. 

37. — Splinter-proofs.      When  troops  are  required  to  remain 


*Cover  from  view  only  can.  of  course,  be  obtain'^d  much  more  quickly,  but  a 
penetrable  cover  is  hardly  more  than  a  target  to  invite  an  enemy's  fire. 


24      Hasty  Intrenchments^  Chin  Pits  and  Epaulements. 

in  the  trenches  for  any  considerable  period,  they  should  be  pro- 
vided with  splinter 'proois  or  shelters  of  some  kind.  Planks,  old 
lumber,  doors,  etc.,  or,  in  their  absence,  small  poles,  may  be  used. 
They  should  be  laid  with  one  end  on  the  embankment,  the  other 
resting  on  the  ground  in  rear  of  the  trench,  and  then  covered  with 
3  or  4  inches  of  earth.  This  defense,  while  not  proof  against  burst- 
ing shells,  will  protect  the  men  from  dropping  bullets  and  shrapnel 
fragments.    (Fig.  4.) 

38. — Concealment  of  shelter  trenches.  Endeavor  should 
always  be  made  to  disguise  the  location  of  shelter  trenches 
by  covering  the  sides  toward  the  enemy  with  branches,  weeds, 
sod,  etc. 

39. — The  advantages  and  disadvantages  of  the  shelters  for 
men  lying  and  kneeling  may  be  briefly  summarized  as  follows: 

Advantages. 

(1)  They  present  but  little  difficulty  to  the  advance  of  the 
defenders'  cavalry  or  artillery  over  them,  and  are  easily  sur 
mounted  by  the  occupants  when  the  advance  is  ordered. 

(2)  They  will  stop  rifle  bullets. 

(3)  They  offer  but  a  small  target  to  the  enemy's  artillery  fire. 

(4)  They  are  quickly  and  easily  made. 
Disadvantages. 

(1)  The  embankments  being  low,  the  field  of  fire  may  be  lim 
ited  by  small  folds  in  the  ground  (care  in  selecting  their  position 
may  partially  remedy  this  disadvantage). 

(2)  In  wet  weather  they  may  become  untenable  by  reason  of 
mud. 

40.— lioop-holes  may  be  provided  by  half  Imbedding  head-logs 
in  the  embankment,  or  resting  them  on  sand-bags  on  top  of  it,  ana 
leaving  spaces  beneath  for  the  rifle.  Or  the  loop-hole  may  be 
formed  with  four  sand-J)ags,  as  shown  In  Fig.  7.  Brushwood  may 
also  be  used  with  an  earth  cover,  either  alone  or  in  connection  with 
a  head-log,  as  shown  in  Fig.  6. 

Loop-holes  for  rifles  splay  inward,  for  field  guns,  outward. 

The  hest  practice  is  not  to  use  JisadAogs  or  loop-holes  (unless  in 
case  of  an  inferior  force  acting  solely  on  the  defensive),  as  their 
use  impels  men  to  hesitate  to  leave  cover  when  the  advance  is 
ordered. 


PLATE  4. 


-ts^ 


FIGURES. 


-»'6"^ 


'^6     Hasty  Intrenchments,  Gun  Pits  and  Epaulements. 

40a. — Cover  for  guns  may  be  obtained  in  two  ways. 

(1)  By  means  of  Chun  Pits;  made  by  digging  a  tiole  of  a  size  suffi- 
cient to  partially  conceal  the  gun  and  gun  detachment,  and  form- 
ing an  embankment  in  front  wuth  the  excavated  earth.  (PI.  4, 
Figs.  1,  2  and  3.)* 

(2)  By  means  of  Chin  Epaulements;  made  by  constructing  an 
embankment  in  front  of  the  gun  which  rests  on  the  natural  surface 
of  the  ground.  In  this  form  the  gun  detachment  would  be  par- 
tially sheltered  in  the  pits  from  which  the  earth  for  the  embank- 
ment is  taken.    (Figs.  4  and  5.) 

Circumstances  would  control  the  selection  of  the  kind  of  cover, 
If  any,  for  field  guns.  The  disadvantages  of  gun  pits  are  the  same 
as  those  of  shelter  trenches,  but  pits  give  more  complete  protection 
to  the  gun.    (See  par.  153.) 


♦Figs.  1,  2  and  4,  PI.  4,  are  from  U.  S.  Artillery  Drill  Regulations. 


PLATES. 


CHAPTER  v.— Clearing  the  Ground. 


41. — The  tools  more  especially  used  in  the  field  may  be  divided 
into  two  classes. 

(1)  Intrenching  tools,  such  as  the  pick,  the  shovel  (long  and 
short  handled,  the  spade,  the  picket  shovel,  and  the  hunting  knife. 

(2)  Cutting  tools,  such  as  the  ax,  the  hand  ax,  the  log  saw, 
the  hand  saw,  the  linked  felling  saw,  the  gabion  knife  (pruning 
knife),  the  hunting  knife,  the  bush  hook  and  the  wire  cutter. 
(PI.  5  and  6.) 

42. — The  choice  of  a  defensive  position  in  which  the  foreground 
is  free  from  obstructions  and  favorable  to  the  defenders'  fire  is  of 
the  utmost  importance:  more  or  less  clearing,  however,  will  usu- 
ally be  necessary.  Clearing  must  be  systematically  done,  and,  as 
in  all  other  work,  should  be  undertaken  by  complete  organizations 
or  parts  of  organizations  under  their  own  officers. 

43.— The  extent  (theoretical)  to  which  the  foreground  should  be 
cleared  is  equal  to  the  effective  range  of  the  defenders'  weapons. 
Practically,  as  wide  a  space  within  this  limit,  is  to  be  cleared,  as 
is  consistent  with  the  time  and  labor  available.  Brushwood  and 
standing  timber  most  often  screen  the  enemy's  advance  and  steps 
should  be  taken  to  remove  them. 

44.— The  tools  usually  employed  in  felling  heavy  timber  are 
the  ax  and  the  log  saw,  the  former  being  the  most  common,  al- 
though inexperienced  men  acquire  familiarity  with  the  latter  more 
quickly.  When  using  the  ax  the  cut  should  be  commenced  on  the 
side  toward  which  it  is  desired  the  tree  should  fall,  ropes  being 
used  to  incline  it  in  that  direction,  if  necessary;  if  immaterial 
which  way  the  tree  falls,  then  attack  it  on  the  side  toward  which 
it  leans;  after  cutting  it  a  little  more  than  half  through  change 
over  to  the  other  side  and  commencing  about  six  inches  higher 
up,  cut  until  it  falls.      In  using  the  saw  it  may  be  necessary  to 


Clearing  the  Grornid.  29 

wedge  the  cut  or  use  other  means  in  order  to  keep  the  saw  free: 
the  teeth  should  be  set  wide. 

Both  saw  and  ax  may  be  used,  in  which  case  the  ax  should  be 
used  on  the  side  toward  which  the  tree  is  to  fall  and  the  saw  on 
the  other  side.    (PI.  6.) 

45. — Trees  would  ordinarily  be  cut  within  a  foot  of  the  ground 
because  a  greater  height  would  afford  cover.  A  man  should  cut 
down  a  hard  wood  tree  1  ft.  in  diameter  in  10  minutes  and  one  of 
soft  wood  of  the  same  size  in  one-third  the  time.  The  hand  ax, 
hand  saw,  and  hunting  knife  are  useful  in  felling  small  trees,  ropes 
being  attached  to  bend  them,  and  the  cut  being  made  on  the 
convex  side. 

Felled  timber  must  be  removed,  if  of  such  a  size  as  to  afford 
shelter  to  the  enemy.  It  is  utilized  in  making  field  casemates, 
magazines,  etc. 

46. — Brushwood  can  be  cleared  at  the  rate  of  about  12  sq.  yards 
per  man  per  hour.  The  men  should  be  extended  at  about  4  paces 
interval,  using  the  bush  hook,  hatchet,  or  hand  ax,  together  with 
the  gabion  or  hunting  knife. 

47. — Grain,  grass,  or  weeds  must  be  trampled  by  men  in  line, 
mowed,  or  burnt. 

48.— Hedges,  fences,  and  walls,  if  not  perpendicular  to  the 
front,  must  be  removed.  Live  hedges  should  be  pulled  to  one  side 
in  order  to  give  the  axmen  greater  freedom.  (PI.  6.)  Fences  can 
ordinarily  be  demolished  with  axes,  walls  by  battering  them  down 
or  blowing  them  down  with  explosives.    (Chapter  XX.) 

Buildings  may  be  battered  down,  burned,  or  demolished  by 
explosives  according  to  circumstances.  In  the  case  of  buildings 
and  walls  it  will  usually  be  necessary  to  remove  the  debris,  which 
can  be  used  for  filling  hollows. 


PLATE  6. 


Cutter. 


Jt — — vvwvvvvvvWw'vvvvvvvv^  Wvvvvvvv^ 


IL,LnkGci  I^eLlLnpr  ScxLv. 


ig 


/KuQTur. 


-^/n/antry    ^p 


ado. 


EUROPEAN. 


.M- 


PLATE' 7.' 


'Figure  1. 


Figure  2, 


Figure  12:    '^^ 


-8- 


CHAPTER  VL—Obstacles. 

49.— Obstacles  have  for  their  object  the  holding  of  the  enemy 
under  fire  while  checliing  his  advance  and  breaking  up  his 
formation. 

(1)  They  must  be  within  the  effective  zone  of  the  defenders*  fire 
and  must  be  so  arranged  as  to  offer  the  least  obstacle  possible  to 
an  advance  from  the  side  of  the  defense. 

(2)  They  must  be  concealed  as  far  as  possible  from  the  view  of 
the  assaulting  party,  so  that  they  may  come  upon  them  as  a 
surprise. 

(3)  They  must  be  diflicult  of  removal  under  fire,  and,  if  possi- 
ble, should  be  of  such  construction  as  will  necessitate  the  use  of 
tools  not  usually  carried  by  troops. 

(4)  They  should,  if  possible,  be  so  placed  as  to  be  secure  from 
the  fire  of  the  enemy's  artillery,  and  so  constructed  that,  if  strtck 
by  his  projectiles,  they  will  suffer  small  damage. 

(5)  They  must  offer  no  shelter  to  the  enemy. 

50.— Abatis,  on  account  of  the  ease  with  which  it  can  be  con- 
structed, is  the  obstacle  most  used. 

It  consists  of  branches  of  trees  about  15  feet  long,  laid  on  the 
ground,  butts  pointing  to  the  rear,  all  small  twigs  being  cut  off,  and 
all  large  branches  pointed  and  interlaced.  ThB  abatis  should  be 
5  feet  high. 

The  branches  are  secured  to  the  ground  by  forks,  wire,  or  by 
logs  laid  over  the  butts  of  the  branches.  The  use  of  wire  to  hold 
down  the  branches  is  recommended,  and  when  used  should  be  also 
passed  from  branch  to  branch  so  as  to  form  an  additional  en- 
tanglement. When  more  than  one  row  of  abatis  is  used  the 
branches  of  one  row  overlap  the  butts  of  the  next  one  in  front. 
(PI.  7,  Figs.  1  and  2.) 

The  abatis  most  easy  of  construction  is  that  made  by  felling 
trees  towards  the  enemy  in  such  manner  as  to  leave  the  fallen 
part  still  attached  to  the  stump;  the  branches  are  then  pointed  as 
described  before.    (Fig.  5.)    This  is  called  slasMng. 

,51.— Abatis  is  often  placed  in  the  front  of  works  when  the 
ditch  is  so  shallow  as  to  present  little  or  no  obstacle  to  an  assault. 
When  so  used  they  are  placed  upright  and  well  tamped  in.  In  all 
cases,  especially  when  small  branches  are  used,  it  is  better  to  sink 


Obstacles.  33 

the  butts  in  triangular  pits,  and,  when  tlie  branclies  are  in  place, 
fill  in  with  earth  and  tamp  well.    (Figs.  3  and  4.) 

In  all  cases  where  exposed  to  artillery  fire  a  glacis  should  be 
constructed  in  front  of  an  abatis,  so  as  to  protect  it  from  injury. 

52. — Low  Wire  entanglements  are  formed  by  driving  into  the 
ground  stakes  projecting  about  18  in.  The  stakes  should  be  driven  in 
rows  about  6  feet  apart,  the  stakes  in  each  row  being  opposite  in- 
tervals in  adjacent  rows.  The  heads  of  the  stakes  are  connected 
by  stout  wire  wound  around  them.  To  make  this  more  effective, 
do  not  clear  the  ground,  but  allow  bushes,  brush,  etc.,  to  remain  in 
place.    (Fig.  6.)    Use  1  ft.  of  wire  to  1  sq.  foot  of  ground  covered. 

53. — High  Wire  entanglements  are  constructed  in  the  same 
manner,  except  that  the  stakes  should  be  at  least  4  ft.  high,  and 
placed  6  to  8  feet  apart.  The  head  of  each  stake  is  connected 
with  the  foot  of  the  stake  diagonally  opposite,  the  line  of  posts  in 
front  and  rear  being  finished  off  as  fence  panels  with  barbed 
wire.  The  use  of  barbed  wire  is  not  advised  for  the  interior 
crossed  work  on  account  of  the  danger  and  difficulty  in  working 
with  it. 

Roughly,  1  yard  of  wire  is  necessary  for  each  square  foot  of 
entanglement.  Ten  men  can  make  about  9  square  yards  of  this 
entanglement  in  one  hour.  This  work  does  not  require  trained 
men.  Wire  entanglement,  either  high  or  low,  is  useful  on  the 
glacis  of  field  works,  as  it  holds  the  attacker  under  fire  at  the  most 
favorable  point.    (Fig.  7.) 

54. — ^Palisades  consist  of  rows  of  trunks  of  trees  or  of  squared 
trunks,  8  or  10  feet  high,  planted  close  together  and  pointed  on 
top.  When  material  is  at  hand,  ribband  pieces  should  be  spiked 
on  the  inside  along  their  tops  about  a  foot  or  two  below  the 
points  to  hold  them  steady.  They  are  used  to  advantage  in  the 
bottoms  of  ditches  or  to  close  the  gorge  of  field  works.  (PI.  8, 
Fig.  1.) 

55. — Praises  are  palisades  arranged  horizontally  or  much  in- 
clined and  are  often  used  at  the  foot  of  the  exterior  slope  and  at 
the  top  of  the  counterscarp;  in  the  first  position  they  point  down 
and  in  the  second  upward.  In  each  case,  the  ribband  or  strip  is 
spiked  on  underneath  and  laid  against  the  ground  near  the  edge  of 
scarp  or  counterscarp,  as  the  case  may  be,  another  one  being  spiked 


PLATE  a 


Obstacles,  35 

to  the  inner  end  of  the  f raise  on  top;  thus  the  outer  ones  give  good 
bearing  surfaces  and  do  not  break  up  the  crest,  and  the  inner  one 
gives  a  bearing  for  staking  and  tying  down.  The  slopes  described 
above  are  given  so  that  unexploded  shell  will  always  roll  away 
from  the  parapet.    (PI.  7,  Figs.  9,  10  and  13.) 

Fraises  may  with  advantage  be  made  of  barbed  wire  in  the 
form  shown,  care  being  taken  that  all  wire  when  finished  is  on 
top  of  the  wooden  supports.  The  advantage  of  this  variety  of 
fraise  is  that  it  is  little  damaged  by  artillery  fire  and  is  very  difll- 
cult  of  removal.     (PI.  7,  Fig.  13.) 

When  time  is  pressing  fraises  may  be  made  of  branches  of  trees 
with  the  butts  well  sunken  and  staked  down.    (PI.  7,  Fig.  12.) 

56. — Crows'  feet,  Chevaux-de-frisey  and  planks  full  of  spikes  have 
been  used  in  the  past  as  obstacles  to  an  advance,  but  the  two 
former  are  not  now  issued  for  use  in  our  service,  and  the  latter  is 
one  not  easily  made  in  the  field.  Such  obstacles  require  much 
time  and  material  in  their  construction  and  are  not  treated  of 
here,  as  they  do  not  fall  properly  in  the  domain  of  Field  Engineer- 
ing; their  value  in  any  event  is  not  commensurate  with  the  diffi- 
culty of  their  preparation.    (PI.  8,  Figs.  2  and  6.) 

57. — Small  Pits  or  troup  de  loup  are  square  on  the  top,  3  feet 
on  a  side,  and  are  pyramidal  in  shape;  they  are  2  ft.  6  in.  deep,  and 
have  a  pointed  picket  driven  in  the  center  of  each. 

In  digging  these  pits  a  glacis  should  be  formed  in  front  of  the 
row  nearest  the  enemy,  and,  to  avoid  filling  the  pits  with  earth 
thrown  from  the  others,  the  row  farthest  from  the  glacis  should 
be  commenced  first.  One  man  can  make  10  pits  per  day  in  easy 
soil.    (PI.  7,  Figs.  8  and  11.) 

Small  pits  may  be  surmounted  by  a  low  wire  entanglement, 
making  a  very  serious  obstacle. 

58. — Fords  may  be  made  impassable  by  strewing  them  with 
harrows,  points  up. 

59. — A  Fougass  is  a  mine  so  arranged  that  upon  explosion  a 
large  mass  of  stones  or  shells  are  projected  towards  the  enemy. 
(PI.  8,  Fig.  3.) 

To  make  a  fougass,  dig  a  hole  in  the  shape  of  a  frustum  of  a 
cone,  inclining  the  axis  in  the  direction  of  the  enemy,  so  as  to 
make  an  angle  with  the  horizon  of  about  45  degrees.     The  sides 


36  Obstacles. 

should  splay  outwards  at  an  inclination  of  12  degrees  from  the 
axis.  The  powder  charge  is  placed  in  the  bottom  of  the  hole- 
preferably  in  a  box— and  in  front  of  this  a  platform  of  wood 
about  3  inches  in  thickness:  on  this  are  piled  stones,  brick,  etc. 
The  mine  is  exploded  by  means  of  electricity  or  common  fuse. 
Care  must  be  taken  in  digging  the  hole  for  the  fougass  that  the 
line  of  least  resistance  is  in  all  cases  in  the  axis  of  the  hole;  to  he 
sure  of  this,  throw  the  excavated  earth  upon  the  crest  towards  the 
defenders'  side  and  ram  well,  allowing  earth  to  enclose  the  sides  of 
the  excavation  in  the  manner  shown  in  cut. 

Fougasses  are  useful  in  defending  boat-landings,  roads,  etc. 

The  following  empirical  formula  may  be  taken  for  determining 
the  charge  of  powder  for  fougasses:  P  =  -^,  in  which  P  and  s 
represent  the  weight  in  pounds  of  the  powder  and  stone. 

When  broken  up,  a  cubic  foot  of  limestone  weighs  96  1T)S. 

60. — Land  Mines  are  small  mines  placed  in  the  line  of  ad- 
vance of  the  enemy  and  exploded  either  by  electricity  or  fuse 
from  the  defense.  The  small  mines  are  made  by  digging  holes 
from  2  to  3  yards  deep,  placing  the  charge  in  a  box  in  a  recess 
excavated  in  one  side  of  the  hole,  and  refilling  with  the  excavated 
earth,  tamping  well.  The  wires  are  carried  back  in  a  small  trench 
to  the  work.  In  common  earth,  the  charge  for  2  yards  deep  is 
about  25  lbs.,  and  for  3  yards  deep  about  80  lbs.;  the  diameter 
of  the  crater  formed  will  be  about  twice  the  depth  of  charge. 
(PI.  8,  Fig.  4.) 

♦To  determine  the  quantity  of  explosive  necessary  for  use  in 
a  **common"  mine,  multiply  eleven-sixths  of  the  cube  of  the  line 
of  least  resistance  in  yards  by  the  quantity  of  explosive  required 
to  throw  out  one  cubic  yard. 

Quantity  of  gunpowder  necessary  to  throw  out  a  cubic  yard  of 
material  (Macaulay):  , 

Pounds.  Ounces. 

Light  sa  ndy  earth 1  13 

Hard  sand 2 

Fat  earth  mixed  with  sand  and  gravel 1  10 

Wet  sand 2         2 

Earth  mixed  with  stone 2         4 


*  "Military  T^and  Mines,"  Mefcur. 


Obstacles.  37 

Pounds.    Ounces. 
Clay  with  tufa 2  8 

Fat  earth  mixed  with  pebbles 2        12 

Rock 3        10 

New  brickwork  or  masonry 2  2 

Inf ^ior  brickwork  or  m-asonry 2        11 

Good  new  brickwork  or  masonry 3        10 

Good  old  brickwork  or  masonry 4        11 

The  following  formula  gives  the  relation  beween  the  charge 
for  common  and  overcharged  or  undercharged  mines: 

C'  =  c  iVs^+Vs)^; 

C  — charge  for  common  mine  (lbs.); 

r  =  radius  of  crater; 

C  =  charge  for  undercharged  or  overcharged  mines  (lbs.) ; 

L  =  length  of  line  of  least  resistance. 

The  following  formulae  give  charges  for  common  mines: 

With  explosive  gelatine, 

C--1-17  (L  +  %  (r  —  L)   )3; 

With  gunpowder, 

e  =  l-10  (L+  %   (r  —  L)   )3; 

C  =  charge  in  pounds; 

r  =  crater  radius  in  feet; 

L  =  line  of  least  resistance  in  feet. 

In  common  mines, 

L-^r. 

61. — Barricades  are  used  to  prevent  the  passage  of  the  enemy 
through  roads,  streets,  and  defiles  generally. 

They  may  be  made  of  any  material  at  hand,  paving  stones, 
overturned  carts,  barrels  filled  with  earth,  stones,  and  articles  of 
like  nature.  They  should  be  built  so  that  a  passage  is  always  left 
for  the  defenders,  but  means  should  be  at  hand  to  close  the  open- 
ing quickly— a  wagon  may  be  used  for  this  purpose,  being  drawn 
away  from  the  opening  when  a  passage  is  desired. 

The  houses  on  either  side  should  be  loop-holed  and  used  to 
flank  the  defense.  Overturned  wagons,  broken  furniture  and 
debris  from  the  adjacent  houses  make  a  very  good  obstacle  and 
should  be  placed  in  front  of  the  barricade  to  ward  off  cavalry 
charges.     (PI.  8,  Pig.  5.) 


PLATE  .9. 


CHAPTER  VII.— Field  Works. 

62. — When  a  position  is  to  be  held  for  a  considerable  period  and 
when  time  is  available,  more  deliberate  defenses  than  the  Hasty 
or  Battle  Intrenchments  (Chapter  IV.)  are  constructed.  These  are 
known  as  Field  Works  and  usually  require  a  minimum  of  6  hours 
for  construction.  The  conditions  to  be  fulfilled,  besides  those  nec- 
essary for  a  defensive  position  (Chapter  1.),  are. 

(1)  That  they  must  afford  protection  against  both  rifle  and 
artillery  fire. 

(2)  That  they  must  be  of  suitable  size  for  the  garrison  that  is 
to  occupy  them. 

(3)  That  they  should  have  suitably  constructed  casemates  to 
shelter  the  garrison  at  night. 

Field  works  may  be  constructed  for  the  defense  of  a  single  ob- 
ject, as  a  bridge,  a  ford,  etc.,  or  they  may  occupy  the  key  points  in 
a  long  line  of  defense,  in  which  case  they  should  be  located  so  as 
to  afford  mutual  protection,  the  intervening  space  either  being  left 
open  or  occupied  by  shelter  trenches. 

Before  proceeding  to  the  study  of  Field  Works,  a  brief  synopsis 
of  the  technical  terms  used  in  connection  with  them  will  be 
necessary. 

63.— A  Parapet  is  a  bank  of  earth  thrown  up  to  cover  the 
defenders  while  firing. 

64. — The  Trace  of  a  work  is  its  outline  in  plan:  the  term  is 
often  applied  to  the  horizontal  projection  of  its  Interior  crest. 
(PI.  9,  Fig.  1.) 

65. — The  Profile  is  a  cross-section  of  the  work  made  by  a  plane 
perpendicular  to  the  interior  crest.    (Fig.  2.) 

In  the  profile,  the  various  parts  are  named  as  follows: 

a.  Banquette  slope,    e.  Exterior  slope.    D.  Ditch. 

b.  Banquette  tread,    f.  Berm.  i.  Interior  slope  of  glacis. 

c.  Interior  slope.         g.  Escarp.  k.  Glacis. 

d.  Superior  slope.       h.  Counterscarp,     t.    Trench. 

66. — The  Interior  Crest  is  the  intersection  of  the  Interior 
and  Superior  slopes:  sometimes  called  the  magistral  line,  ("a" 
Fig.  1.) 


40  Field  Works. 

67.— The  Exterior  Crest— that  of  the  Superior  and  Exterior 
slopes.  C'b*'  Fig.  1.)  The  thickness  of  parapet  is  the  horizontal 
distance  between  interior  and  exterior  crests. 

68. — A  Traverse  is  a  bank  of  earth  inside  a  work  to  protect 
some  portion  of  it  from  direct  fire.  When  the  protection  afforded 
is  from  reverse  fire,  the  traverse  is  sometimes  called  a  Parados. 
(Figs.  8  and  4.) 

69. — An  Embrasure  is  a  revetted  opening  in  the  parapet, 
through  which  field  guns  may  fire.  It  is  said  to  be  Direct  or 
Oblique  according  to  whether  its  axis  is  perpendicular  or  inclined 
to  the  line  of  parapet. 

70. — A  Gun  Bank  is  a  raised  mound,  by  means  of  which  Held 
guns  may  fire  over  the  parapet.  Guns  thus  placed  are  said  to  be 
en  barbette. 

The  relative  advantages  of  Embrasures  and  Gun  Banks  are  as 
follows:— 

Embrasures  afford  greater  protection  to  the  gunners,  but 

(a)  They  afford  a  very  limited  field  of  fire. 

(b)  They  weaken  the  parapet  and  require  frequent  repairs. 

(c)  The  place  of  the  gun  when  not  in  action  cannot  well  be  used 
by  Infantry. 

The  conditions  as  to  Gun  Banks  are  the  converse  in  each  case. 

71. — The  Command  of  a  work  is  the  height  of  its  interior  crest 
above  the  ground  on  which  it  is  constructed,    ("m"  Fig.  2.) 

72.— Its  Relief  is  the  height  above  the  bottom  of  the  ditch, 
("o"  Fig.  2.) 

73.— The  Plane  of  Site  is  a  plane  tangent  to  the  ground  on 
which  the  work  is  constructed. 

74. — The  Terreplein  is  the  surface  of  the  ground  inside  the 
work  and  does  not,  of  necessity,  coincide  with  the  plane  of  site, 
since  the  whole  interior  of  the  work— i.  t'.,  the  terreplein— may  be 
lowered  for  the  purpose  of  securing  more  cover. 

When  the  banquette  tread  is  more  than  2  feet  above  the  terre- 
plein, its  slope  may  be  stepped  with  fascines  or  planks:  this  has 
the  advantage  of  giving  more  interior  space,  but  tends  to  produce 
confusion  on  the  part  of  the  defenders,  especially  in  a  night 
assault. 


Field  Works.  41 

75. — The  interior  slope  is  usually  made  as  steep,  up  to  four  on 
one,  as  the  revetment  will  stand. 

76. — The  superior  slope  is  necessary  in  order  to  secure  the  best 
fire  effect  on  the  ground  immediately  in  front  of  the  work.  It 
weakens  the  parapet  near  the  interior  crest,  however,  and  this 
defect  increases  as  the  slope  is  made  steeper;  hence,  it  should  be 
as  slight  as  is  consistent  with  good  fire  effect. 

The  degree  of  this  slope  is  regulated  by  the  principle  that  fire 
from  rifles  resting  on  its  surface  should  not  pass  more  than  three 
feet  above  the  glacis,  or,  when  there  is  no  glacis,  above  the  outer 
edge  of  the  ditch.    It  will  thus  depend  on 

(1)  The  command  of  the  work. 

(2)  The  inclination  of  the  plane  of  site. 

(3)  The  distance  from  the  interior  crest  to  outer  edge  of  ditch. 
The  slope  should  not  exceed  one  on  four;  one  on  six  (normal)  is 

better,  and  then,  if  necessary,  make  a  glacis  of  the  requisite 
height. 

77.— The  exterior  slope  should  be  as  gentle  as  two  on  three,  if 
possible,  owing  to  the  fact  that  steeper  slopes  are  soon  destroyed 
by  artillery  fire. 

78. — The  Berm  may  be  as  great  as  6  ft.  in  width;  ordinarily  it 
would  not  be  greater  than  2  ft.,  while  in  favorable  soil  none  may 
be  left  at  all. 

Advantages  of  berm: 

(1)  It  relieves  the  edge  of  the  ditch  from  the  weight  of  the  par- 
apet and  thus  prevents  caving,  in  loose  soil. 

(2)  It  enables  the  parapet  to  be  thickened. 
Disadvantages: 

(1)  It  affords  a  footing  in  an  assault.  (This,  however,  may  be 
partially  remedied  by  use  of  obstacles.) 

79. — The  slope  of  the  escarp  and  counterscarp  should  be  equal 
to  or  greater  than  the  exterior  slope,  the  counterscarp  being  as 
steep  as  the  earth  will  stand. 

80.— The  Glacis  snould  be  parallel  to  the  superior  slope,  in 
order  to  get  the  best  fire  effect  from  the  crest. 

81. — If  the  parapet  does  not  require  much  earth,  and  the  ditch 
is  required  as  an  obstacle,  it  may  be  made  triangular  in  cross-sec- 


42  Field  Works. 

tion.  This  form  gives  ,the  greatest  depth  and  prevents  the  assail- 
ants from  forming  in  the  ditch,  but  it  is  difficult  of  construction. 
Eight  feet  may  be  talven  as  the  extreme  depth  of  ditch  and  twelve 
feet  as  the  extreme  lieight  of  parapet.  The'  width  of  the  ditch 
varies  with  the  amount  of  earth  required— 12  ft.  at  the  top  being 
a  minimum. 

A  parapet  with  trench  and  ditch  affords  cover  iu  the  shortest 
time  possible:  each  foot  of  depth  in  the  trench  means  2  ft.  of 
cover,  plus  the  additional  protection  afforded  by  the  earth  from 
the  ditch. 

A  parapet  with  ditch  alone  affords  greater  cover  to  the  ground 
in  rear  and  better  command  of  ground  in  front,  but  its  height 
makes  it  more  conspicuous. 

82.— Referring  to  traces  of  various  works  (PI.  9,  Fig.  5)— 

a,  is  a  salient  angle. 
a'   is  a  shoulder  angle. 

b,  is  a  reentrant  angle. 

c,  c,  c,  are  faces.  e,  e,  is  the  gorge. 

d,  d,  d,    are  flanks.  f,    is  the  capital. 
83. — Field    Works    are    classified    with    reference    to    their 

trace,  as 

(1)  Open,  which  have  thick  parapets  on  exposed  sides,  the  rear 
or  gorge  being  open. 

(2)  Closed,  in  which  the  thick  parapet  is  continuous. 

(3)  Half-Closed,  which  only  differ  from  the  "open"  in  that 
the  gorge  is  closed  by  obstacles,  stockade  work,  or  shelter 
trenches. 

Advanced  works  within  rifle  range  of  the  main  defensive  line, 
as  well  as  those  in  positions  where  the  flanks  are  secure  (as  a 
bridge  head),  should  usually  be  "open."  Works  in  main  line  and 
advanced  works  beyond  rifle  range  should  be  "half-closed";  those 
in  isolated  positions  or  on  the  flanks  of  a  defensive  line— "closed." 

Open  works  have  the  advantage  over  closed,  of  affording  greater 
freedom  of  movement  to  the  defenders,  and,  in  the  event  of  cap- 
ture, of  being  exposed  to  fire  and  assault  from  the  works  in  rear. 

Closed  works,  while  affording  greater  protection  from  assault, 
are  liable  to  have  their  parapets  exposed  to  enfilade  or  reverse  fire, 
besides  which  the  available  interior  space  is  much  reduced. 


PLATE  10. 


44  Field  Works. 

84.— Forts  and  Redoubts  (Closed  Works)  are  distinguished 
by  tlie  former  having  reentering  angles,  thus  affording  defense 
of  the  ditch  from  the  parapet,  both  conditions  being  lacking  in 
redoubts. 

Redoubts,  as  compared  to  forts,  are  of  simpler  trace,  do  not  re- 
quire so  large  a  garrison,  and  afford  better  frontal  fire;  but,  as 
they  have  no  ditch  defense  (unless  caponiers  and  counterscarp 
galleries  are  constructed),  they  should  be  traced  to  support  one 
another. 

85. — With  respect  to  caponiers  (PI.  20)  and  counterscarp  gal- 
leries—the former,  if  sunken,  as  is  usually  necessary  for  protection 
against  artillery  fire,  may  become  untenable  in  rainy  weather; 
while  communication  with  the  latter  is  diflicult  and  may,  by  the 
enemy,  be  rendered  impossible.  The  objections  to  these  forms  of 
ditch  defense  are  so  great,  and  their  use  so  limited,  where  proper 
frontal  fire  and  obstacles  are  possible,  that  their  construction  is 
seldom  necessary. 

86.— The  Sector  of  Fire  is  a  term  used  to  designate  the  angular 
space  in  front  of  a  work  which  is  swept  by  its  fire  (30°  on  each 
side  of  a  perpendicular  being  considered  the  limit  of  oblique  rifle 
fire.)  Thus,  a  straight  line  of  parapet  has  a  sector  of  fire  of  60° 
(PI.  10,  Fig.  1),  while,  in  a  redan,  it  varies  with  the  angle  at  the 
salient.  With  a  salient  of  120°,  the  sector  of  fire  is  evidently  120° 
(Fig.  2);  with  a  60°  salient,  there  will  be  an  undefended  space  of 
60°.  (Fig.  3.)  This  undefended  space  may  be  done  away  with  by 
blunting  the  redan.  (Fig.  4.)  A  redan  with  shoulder  angles 
(Fig.  5)  furnishes  a  ditch  defense  in  front  of  the  shoulders  and  does 
away  with  part  of  the  dead  space  in  front  of  the  salient,  but  it  is 
diflicult  of  construction  and  is  not  usually  resorted  to. 

87.— For  reasons  given  in  Chapter  XI.,  it  is  often  desirable  to 
place  the  guns  outside  the  work;  in  which  case  some  plan  like 
Fig.  6  may  be  adopted,  the  single  line  representing  a  shelter 
trench. 

88.— Defilade  of  Field  Works.  In  order  that  Field  Works  may 
fulfill  the  condition  of  screening  the  occupants  from  the  fire  and 
view  of  an  enemy,  the  problem  of  defilade  arises. 

This  may  be  defined  as  the  operation  of  regulating  the  direction 
and  command  of  the  earth  cover  so  that  the  interior  of  the  work 
is  protected  from  the  direct  fire  of  an  enemy. 


Field  Works.  45 

The  problem  resolves  itself  into  two  distinct  parts— 

(1)  Dcfiladiny  in  plan, 

(2)  Defilading  in  section. 

89. — Defilading  in  plan.  This  involves  the  selection  of  the 
trace  of  the  work  (its  position  having  been  previously  chosen). 
The  trace  will  vary  with  the  plane  of  site,  the  terrain  in  the  im- 
mediate vicinity,  the  proximity  of  high  ground  that  the  enemy 
may  occupy,  and  the  time  available  for  construction.  A  plane  of 
site  sloping  to  the  rear  is  obviously  the  easiest  to^  defilade,  and 
one  sloping  toward  the  enemy  the  most  difficult.  Salients  should 
occupy  commanding  ground,  the  lower  portion  being  taken  for 
the  reentrants  or  for  the  gorge.  The  longer  faces  of  a  work  should 
lie  in  the  direction  of  lower  or  inaccessible  ground,  so  that  they 
cannot  be  enfiladed. 

With  commanding  ground  in  front,  the  work  is  more  difficult 
to  defilade  in  proportion  to  its  depth;  therefore,  have  longer  faces 
opposed  to  the  high  ground  and  make  the  work  as  shallow  as  is 
consistent  with  other  conditions. 

As  a  rule,  the  longer  faces  of  a  work  must  lie  so  that  the  de- 
fenders can  bring  as  direct  a  fire  as  possible  in  the  direction  of 
expected  attack. 

All  the  foregoing  conditions  as  to  defilading  in  plan  cannot,  in 
the  usual  case,  be  satisfied,  but  the  object  to  be  attained  must  be 
kept  constantly  in  view,  and,  in  selecting  the  trace  for  a  work,  an 
officer's  ability  will  be  shown  by  the  skill  with  which  he  harmon- 
izes the  various  diverse  requirements. 

After  the  careful  selection  of  the  trace,  as  already  indicated, 
and  marking  it  by  pickets,  the  problem  is  completed  by  defilading 
tlie  proposed  work  in  section. 

90. — Defilading  in  section*  With  a  horizontal  site  and  only 
level  ground  toward  the  enemy,  a  constant  command  of  8  ft.  is 
sufficient  to  protect  the  whole  interior  of  the  work. 

On  an  irregular  site,  or  when  necessary  to  place  a  work  in  a 
position  commanded  by  higher  accessible  ground,  the  necessary 
protection  of  8  ft.  may  be  attained  in  one  of  three  ways— 

(1)  By  raising  a  parapet. 

<2)  By  lowering  the  terreplein. 

(3)  By  use  of  traverses,  parados,  bonnets,  etc. 


FTrATE  11 


Pi^re  1. 


^   Plani^4-  -^#^-  -  "■-  ;^V 


Figure.  2. 


Figure  3. 


^J;QK 


Figure  4, 


Field  Works.  47 

To  determiue  bow  niucli  protection  is  needed,  suppose,  for  ex- 
ample, the  proposed  worli  is  a  lunette.  Plant  poles  at  the  salients 
of  sufficient  length  to  reach  the  interior  crest  of  completed  work. 
Place  two  pickets  at  the  gorge,  about  G  ft.  apart,  .one  on  each  side 
of  the  capital,  and  a  third  8  ft.  to  the  front.  Tie  a  string  to  the 
rear  pickets,  3.5  ft.  from  the  ground,  the  string  passing  round  the 
third  stake.  (PI.  11,  Fig.  2.)  Taking  position  behind  the  horizontal 
string,  have  an  assistant  move  the  string  on  the  forward  picket 
until  it  comes  into  the  plane  fixed  by  the  eye,  the  horizontal  string 
and  the  highest  point  of  the  dangerous  ground.  This  plane, 
which  is  now  established  by  the  string  triangle,  is  called  the  tan- 
f/cnt  plane.  A  plane  parallel  to  this  and  4.5  ft.  above  it  is  l^nown 
as  the  plane  of  defilade.  (Fig.  1.)  The  proper  height  of  parapet  at 
the  salient  and  shoulder  angles  is  now  fixed  by  sawing  off  the 
poles  4.5  ft.  above  the  points  in  which  the  tangent  plane  cuts  them. 
This  will  evidently  give  8  ft.  cover  at  the  gorge,  at  which  point 
the  height  of  parapet  of  the  flanks  is  8  ft. 

If  it  is  found  that  the  required  height  of  parapet  exceeds  12  ft., 
the  plane  of  defilade  may  be  lowered  not  to  exceed  1.5  ft.  This  will 
still  give  6.5  ft.  protection  at  the  gorge. 

If  this  proves  insuflicient,  either  traverses  must  be  resorted  to 
or  the  terreplein  at  the  gorge  lowered. 

91. — To  defilade  a  work  from  two  or  more  heights,  the  plane 
must  be  tangent  to  the  two  heights  to  which  angles  of  elevation 
are  the  greatest.  As  three  points  fix  a  plane,  it  follows  that  the 
tangent  plane  would  usually  contain  but  a  single  point  of  the' 
string  at  the  gorge;  hence,  the  problem  is  solved  by  reversing  the 
string  triangle — i.  e.,  fixing  the  apex  at  the  gorge  3.5  ft.  above-  the 
ground,  and  the  two  extremities  of  the  base  within  the  proposed 
work  and  far  enough  apart  to  allow  the  two  heights  to  be  seen 
between  them.  An  assistant  at  each  of  the  forward  stakes  ad- 
justs the  string  as  directed.  (Fig.  3.)  The  problem  is  then  com- 
pleted as  in  the  previous  case. 

92. — It  is  sometimes  advisable,  when  a  single  plane  of  defilade 
gives  too  great  a  command,  to  use  two  planes;  the  portion  of  the 
interior  of  the  work  on  the  side  tow^ard  H  (Fi^.  4)  being  defiladed 
from  it,  and  that  on  the  other  side  from  the  height  H'.  This 
method  exposes  the  faces  and  flanks  to  reverse  fire  and  renders 
traverses  (parados)  necessary. 


48  Field  Works. 

93.— The  height  of  a  traverse  (which  should  be  such  that  a 
shot  grazing  it  will  pass  2  ft.  above  the  parapet  it  is  to  cover)  is 
found  as  follows: 

Assume  that  the  traverse  is  to  be  on  the  capital  of  a  lunette. 

The  problem  of  direct  defilade  with  two  planes  having  been 
solved,  and  the  poles  at  angles  of  the  works  having  been  sawed  off 
to  indicate  the  proper  height  of  interior  crest  in  order  to  defilade 
the  work  as  far  as  the  capital,  the  height  of  traverse  to  protect  a 
flank  from  reverse  fire  is  found  thus:  Measure  down  from  the 
tops  of  the  poles  at  the  extremities  of  the  flank  any  convenient  dis- 
tance, as  3  feet,*  mark  the  points  and  connect  them  by  a  string. 
This  string  and  the  opposite  height  determine  a  plane  which  will 
cut  rods  held  vertically  on  the  capital,  at  a  distance  of  5  feet  below 
the  required  top  of  the  traverse  (2  ft.  plus  the  distance  measured 
down  on  the  poles).  Proceed  in  a  similar  manner,  using  the  other 
hill  and  its  opposite  flank.  The  greater  of  the  two  results  fixes 
the  height  of  that  portion  of  the  traverse.  In  the  same  manner. 
Its  height  to  protect  the  faces  from  reverse  fire  may  be  found. 
By  reference  to  Fig.  4  this  will  be  readily  understood. 

This  method,  while  not  absolutely  accurate,  will  give  results 
near  enough  for  all  practical  purposes,  with  the  error  on  the  side 
of  safety.  Traverses  or  Parados  are  the  usual  protection  against 
reverse  and  enfilade  fire,  and,  although  sometimes  used  to  protect 
parts  of  a  work  from  direct  fire,  this  is  usually  attained  either  by 
raising  the  parapet,  by  lowering  the  terreplein,  or  by  both  these 
methods  combined. 

94.— Profiling.  After  the  trace  of  the  work  has  been  decided 
upon,  the  problem  of  defilade  solved,  the  poles  at  the  angles  cut 
off  as  indicated,  and  the  cross-section  of  the  parapet  decided  upon, 
the  next  step  is  to  erect  profiles  which  shall  correspond  to  this 
cross-section.  These  profiles  are,  if  practicable,  to  be  made  of 
strips  or  battens  1  in.  x  2  in.,  and  placed  at  intervals  of  about  10 
yds.  along  each  face  and  flank,  as  well  as  at  each  angle. 

For  parapets  not  over  6  ft.  in  height,  stakes  may  at  once  be 
driven  into  the  ground  and  strips  nailed  to  them,  but  for  higher 
parapets  it  is  more  convenient  to  make  the  profile  on  the  ground, 
merely  driving  short  pickets  in  place  of  the  long  stakes  In  the  first 


*The  idea  beinsf  to  have  the  string:  behind  which  the  observer  stands,  when 
looking  towards  the  height,  at  about  the  level  of  the  eye. 


PLATE  12. 


PLATE '13 


CJi  N  N  O  o 

.<0  »fi   T-    o    o 

■  -^  o  <^-  ^  ^ 


C  ^  o-d  <3> 


m 


Field  Works.  51 

Instance.  When  completed,  the  profile  is  up-ended  and  nailed  to 
the  pickets.  (Fl.  12,  Fig.  1.)  If  strips  cannot  be  obtained,  the 
entire  profile,  except  the  uprights,  may  be  made  of  twine.  The 
profiles  at  the  angles  of  the  works,  known  as  oblique  or  angle  pro- 
files, will  evidently  differ  from  the  others  in  length,  while  their 
height,  on  level  ground,  remains  the  same.  The  position  of  any 
point  of  the  angle  profile,  as,  for  example,  the  exterior  crest,  is 
fixed  by  finding  the  intersection  of  the  prolonged  exterior  crest 
lines  of  the  face  profiles.  This  result  is  accomplished  by  standing 
on  the  farther  side  of  the  second  profile  from  the  angle  and  lin- 
ing in  an  assistant  who  holds  a  rod  vertically  at  the  angle,  one  end 
of  the  rod  resting  on  the  ground.  After  the  profiles  are  in  place, 
twine  should  be  stretched  between  them  to  indicate  the  various 
crest  lines.  The  outer  edge  of  the  battens  marks  the  extent  of 
the  fill,  except  in  the  case  of  the  interior  slope,  which  is  marked  by 
the  inner  edge  when  the  slope  is  to  be  revetted. 

95. — Calculation  of  Dimensions  of  Earthworks.  Tfie  Com- 
mand of  the  proposed  work  having  been  fixed  by  the  requirements 
of  defilade,  and  the  thickness  by  the  character  of  fire  expected, 
it  becomes  nece>ssary  to  calcailate  the  dimensions  of  the  excavations, 
so  that  theij  ivill  furnish  enough,  and  no  more,  earth  than  is  required. 
The  size  of  embankments  and  trench  are,  by  the  nature  of  the 
problem,  fixed,  as  is  the  depth  of  ditch;  hence  the  only  variable  is 
width  of  ditch,  which  is  found  as  follows: 

Assuming  the  relief  to  be  constant  and  the  profile,  for  example, 
to  be  as  shown  in  PI.  13,  make  a  sectional  sketch  of  the  proposed 
work  at  any  point  except  an  angle.  Calculate  the  sectional  area 
of  parapet,  glacis,  and  trench,  in  square  feet,  and  from  the  sum  of 
the  first  two  subtract  the  last:  the  remainder  divided  by  the  as- 
sumed depth  of  ditch,  in  feet,  will  give  the  mean  width  of  ditch, 
from  which,  knowing  the  slope  of  escarp  and  counterscarp, 
the  width  at  top  and  bottom  can  readily  be  found. 

96.— Earth  in  embankment  occupies,  for  a  time,  about  one- 
twelfth  more  space  than  it  did  originally  if  untamped,  but  this  In- 
crease is  not  usually  taken  into  account  in  the  computations  for 
ascertaining  the  width  of  ditch.  If  the  earth  is  tamped  it  occupies 
about  1-10  less  space.  When  the  relief  of  a  work  is  not  constant, 
It  is  evident  that,  in  order  to  get  the  proper  amount  of  earth, 


52  Field  Works. 

either  the  depth  or  the  width  of  ditch  must  vary.  On  account  of 
the  labor  required  in  raising  earth,  the  limit  of  depth  is  taken  at 
8  ft;  for  a  similar  reason,  the  maximum  height  of  parapet  is 
taken  at  12  ft.  Whatever  the  depth  of  ditch  assumed,  it  is  always 
constant.  The  required  width  at  any  point  is  found  by  means  of 
a  section  of  the  work,  as  already  explained,  a  section  near  the 
extremities  of  each  face  determining  the  wudth  of  ditch  for  that 
entire  face. 

97. — An  excess  of  earth  will  occur  at  the  salients  and  a  defi- 
ciency at  the  reentrants,  although  this  may  be  partially  obviated 
by  making  the  shovelers  throw  toward  the  reentrants. 

98. — Drainage  of  the  trench  must  be  provided  for  at  the  time 
the  work  is  constructed.  If  the  fall  is  toward  the  gorge,  an  open 
drain  will  suffice;  but  if  in  any  other  direction,  a  covered  draiu 
(PI.  50)  should  be  left  to  carry  the  water  to  the  ditch. 

Construction  of  Field  Works.  The  details  of  construction 
and  dimensions  of  earthworks  will  change  with  varying  require- 
ments and  soil,  but  there  are  certain  general  principles  that 
should  be  followed  in  all. 

99.— As  to  profile:  The  Normal  (PI.  14,  Fig.  2)  fulfills  the 
conditions  as  to  simplicity,  protection  against  field  artillery  (in 
most  soils),  command  of  the  ground  in  front,  and  cover  stand- 
ing, in  the  trench.  The  trench  is  stepped  and  steps  revetted  to 
facilitate  mounting  the  banquette,  while  the  berm  is  omitted  to 
deprive  the  assailants  of  a  foothold.  The  command  may  be  in- 
creased either  with  or  without  constant  relief,  the  parapet  thick- 
ened or  reduced,  and  the  trench  made  into  a  casemate  without 
changing  the  type  of  this  profile. 

100.— As  to  garrison:  For  ordinary  field  works,  the  garri- 
son is  usually  computed  at  2  men  per  yard  of  interior  crest;  but 
for  isolated  works,  this  estimate  should  be  increased  by  one-half. 
Embrasures  and  gun-banks  each  reduce  the  interior  crest  line 
available  for  troops,  by  5  yards. 

101. — As  to  laying  out  tasks:  Cutting  lines  must  be  marked 
by  tape  or  pick,  computations  made,  and  the  exact  size  of  the  task 
for  each  relief  determined  in  accordance  with  the  rules  given  in 
Chapter  VIII. 

As  an  example  of  laying  out  tasks,  assume  that  an  earthwork 


PLATE  14. 


PIATE  15. 


Field  Works.  55 

with  normal  profile  and  constant  command  of  6  ft.  is  to  be  made 
on  a  level  site. 

Before  work  is  commenced,  the  outer  and  the  cutting  lines  of 
ditch  and  trench  must  be  marked.  As  fatigue  parties  cannot  be 
expected  to  excavate  eartii  and  at  the  same  time  preserve  the 
proper  slopes,  the  usual  method  followed  is  to  dig  vertically  as  in 
dicated  by  the  cutting  lines  and  afterward  form  the  slopes  by  cut 
ting  off  the  steps. 

The  cutting  lines  for  the  task  of  the  1st  Relief  would  be  made 
oil  the  ground,  as  indicated  in  section  and  plan.  (PI.  14,  Fig.  1.) 
The  1st  Relief  having  finished,  cutting  lines  for  task  of  2d  Relief 
would  then  be  marked  out;  and  finally,  the  3d  Relief  would  com- 
plete the  slopes  of  ditch  and  parapet,  and  finish  any  work  not  com- 
pleted by  the  other  reliefs. 

When  not  practicable  to  revet  the  banquette  and  trench  steps, 
the  risers  may  be  sloped  back  at  about  six  on  one. 

When  necessary  to  throw  earth  more  than  12  ft.  horizontally, 
extra  shovelers  should  be  provided  at  the  rate  of  1  to  each  2,  or  2 
to  each  3  diggers,  depending  upon  the  soil  and  the  distance  it  is  to 
be  thrown. 

102.— Gun-banks,  when  made,  are  usually  placed  in  the  sali- 
ents, for  the  reasons  that  the  guns  will  have  a  greater  field  of 
fire  and  it  is  at  this  point  that  the  earth  of  which  they  are  made  is 
in  excess.  PI.  12,  Fig.  2  shows  a  gun-bank  on  a  straight  line  of 
parapet,  and  Fig.  3  one  at  a  salient.  The  top  is  horizontal  and  3.5 
ft.  below  the  interior  crest:  this  distance  may  vary,  however,  for 
different  pieces.  All  slopes  are  one  on  one,  except  the  ramp,  or 
roadway  leading  up  to  the  bank;  this  may  be  as  steep  as  one  on 
four,  but  a  gentler  slope  is  better.  The  width  of  ramp  should  be  8 
ft.  The  level  surface  of  the  bank  extends  back  24  ft.  from  the  para- 
pet and  a  log  or  fascine  is  half  sunken  and  picketed  near  the  front, 
for  a  hurter.  The  width  of  bank  for  a  single  gun  is  15  ft.  At  a  sali- 
ent (PI.  12,  Figs.  3  and  4)  the  angle  is  filled  in  by  a  straight  revet- 
ment from  6  ft.  to  15  ft.  long  and  the  superior  slope  reduced  to  cor- 
respond to  lines  joining  its  extremities  with  the  exterior  crest 
salient.    This  forms  what  is  known  as  a  "pan  coup6." 

103. — Embrasures  for  field  guns  would  be  used  in  positions 
where  the  fire  is  required  to  be  in  one  direction  only;  for  example, 


56  Field  Works, 

to  sweep  a  road,  bridge,  or  ford;  or  in  the  flank  of  a  work  to 
cover  ground  in  front  of  an  adjacent  work. 

PI.  15,  Fig.  1,  shows  the  horizontal  projection  and  the  section  of 
an  embrasure.  It  is  made  at  the  same  time  as  the  parapet,  by 
making  the  sole  "s"  parallel  to  the  superior  slope.  The  cheeks, 
"c,  c,"  are  vertical  at  the  throat,  "e,"  and  have  a  slope  of  one  on 
one  at  the  other  extremity;  their  height  should  never  exceed  4  ft. 

The  usual  method  of  forming  an  embrasure  is  to  stretch  a  string 
nlong  the  line  of  fire;  at  the  throat  lay  off  1  ft.  on  each  side  of  it, 
and  at  a  distance  of  5  ft.  from  the  throat  lay  off  1.5  ft.  in  a  similar 
manner.  Right  lines  joining  the  corresponding  points  so  deter- 
mined will  mark  the  outer  lines  of  the  sole,  which  will  splay  one 
on  ten.  Each  throat  gabion  is  vertical,  the  extreme  ones  being  in- 
clined throe  on  one;  the  slope  of  the  intermediate  ones  is  secured 
by  alignment  top  and  bottom  on  the  extreme  ones.  Each  gabion 
is  anchored  independently  of  the  others,  so  that  one  may  be  torn 
out  without  seriously  injuring  the  embrasure. 

104. — By  the  Merlon  is  meant  that  portion  of  the  parapet  be- 
tween two  embrasures  and  above  the  soles.  Embrasures  should, 
as  a  rule,  never  be  closer  together  than  15  ft. ;  otherwise  the  merlon 
is  too  mucli  weakened. 


PLATE  16. 


Fig-l. 


Fio.3. 


i  ',    1 

i  '  I     ■ 


'4'^" 

5' 


5' 

:5" 

^' 

5* 

6' 


"3^' 

4'  4-'  4-'  4'  4' 


Fig.4, 


0 

* 


'^, 


CHAPTER  VIII.— Working  Parties. 

Occasion  may  arise,  as,  tor  example,  at  night,  in  the  presence  of 
an  enemy  or  even  with  a  large  working  party,  when  a  well-estab- 
lished system  of  talking  and  uandling  tools,  distributing  and  reliev 
ing  worlving  parties,  etc.,  will  be  a  paramount  importance. 

105. — Organization  of  Working  Parties.  The  nature  of  the 
required  worlv  having  been  decided  upon,  the  estimate  of  and  the 
application  for  the  requisite  number  of  men  and  tools  devolves 
upon  the  officer  charged  with  its  execution. 

A  working  party  of  the  requisite  strength  (which  should  include 
a  reserve  of  1-lOth)  should  be  furnished,  as  far  as  possible,  from  a 
complete  organization,  a  company,  a  battalion  or  brigade,  and  not 
from  detachments  of  different  organizations. 

106. — Responsibility.  The  party  should  be  divided  into  re- 
liefs and  the  task  each  is  to  accomplish  made  plain  before  it  begins 
work.  Tlie  officers  and  non-commissioned  officers  of  the  working 
party  are  responsible  for  the  amount  of  work  done. 

107. — Taking  Tools.  The  first  relief,  having  been  formed 
in  single  rank  with  rifles  slung  across  the  back,  is  marched  to  the 
parli  where  the  tools  have  previously  been  laid  out,  either  in  rows 
(PI.  16,  Fig.  1)  or  in  heaps.  (Fig.  2.)  The  relief  in  the  former  case 
is  advanced  in  line  to  the  row  and  each  takes  a  pick  in  the  left 
and  a  spade  in  the  right  hand;  in  the  latter  case  the  party  in  col- 
umn of  files  is  marched  between  the  piles,  each  in  turn  receiving 
a  pick  in  the  left  and  a  spade  in  the  right  hand.  The  relief  is 
then  marched  in  column  of  fours  or  twos  to  the  point  where  the 
work  is  to  begin. 

108. — Carrying  Tools.  In  carrying  picks  and  spades  the 
handles  are  grasped  near  the  iron,  which  is  held  vertically,  the 
arras  extended  and  the  hands  close  to  the  side.  In  turning,  the 
point  of  the  pick  should  be  lowered  and  the  blade  of  the  shovel 
raised,  and  when  marching,  either  in  line  or  in  column,  the  han- 
dles should  be  splayed  outward,  in  order  to  prevent  interference. 
The  necessity  undei*  certain  circumstances  of  preserving  silence 
makes  the  above  precautions  important  at  all  times  as  a  matter  of 
training. 


Working  Parties.  59 

109. — Extending  the  Working  Party.  VVlieu  tlie  tirst  re- 
lief approaclies  the  designated  point  it  is  lialted,  ttien  brolten  in- 
to column  of  Hies  and  direction  cnanged,  if  necessary,  so  tiiat  tlie 
iiead  of  tlie  column  approaclies  in  a  direction  parallel  to  and  about 
3  yds.  in  rear  of  tlie  tape  marking  tiie  front  edge  of  proposed  exca- 
vation. (Fig.  3.)  When  the  leading  tile  is  opposite  his  place  the 
command  is  given: 

{1)  On  riylit  (or  lojtj  into  line  at  tico  paces  inter  vat.  (2)  March. 
(3)  Detachment.    (4)  Halt. 

The  command  "Halt"  is  given  when  the  leading  file  is  1  yd.  iu 
rear  of  the  tape.  While  the  line  is  forming,  the  correct  positions 
are  at  once  taken,  as  follows: 

Each  man  on  arriving  at  the  line  extends  his  arms  horizontally, 
holding  them  thus  until  his  own  position  and  that  of  the  man  fol- 
lowing him  are  established  by  touching  hands.  As  soon  as  each 
man  has  his  position  he  drives  his  pick  into  the  ground  on  the  left 
of  his  own  task  and  lays  his  shovel  on  the  ground,  parallel  to  and 
at  a  distance  in  the  rear  of  the  tape  equal  to  the  width  of  his  task 
from  front  to  rear. 

Rifles  are  then  unslung,  belts  and  canteens  removed,  and  all 
having  been  placed  on  the  ground  three  paces  directly  to  the  rear 
of  task,  butts  of  rifles  toward  the  front,  the  men  sit  or  lie  down  be- 
hind their  shovels  until  the  order  ^'Commence  work," 

110.— Extension  of  2d  and  3d  Reliefs.  Each  man  of  the  1st 
relief,  after  completing  his  task,  scrapes  his  tools  and  lays  them 
together  in  rear  of  the  trench. 

The  task  being  completed,  each  man  secures  his  accoutrements 
and  rifle,  and  then,  under  direction  of  his  officers,  closes  in  to  the 
left  (or  right),  forming  column  of  fours,  which  is  then  marched 
back  to  camp. 

As  an  incentive  to  rapid  work,  each  relief  should  be  allowed  to 
return  to  camp  on  the  completion  of  its  task. 

If  the  working  party  be  large  and  the  work  of  a  complicated 
nature,  each  relief  should  arrive  in  successive  detachments  and 
their  location  on  the  work  should  have  been  previously  designated, 
so  that  there  need  be  no  delay  or  confusion,  even  at  night. 

Work  should  not  be  commenced  until  the  distribution  of  the 
entire  relief  is  complete,  since  any  change  after  work  has  begun 
tends  to  confusion,  loss  of  tools,  and  delay. 


60  Working  Parties. 

111.— -Tasks.  An  untrained  workman  can  excavate  in  ordi- 
nary soil  one  cubic  yard  of  eartli  per  liour  for  four  consecutive 
liours.  As  some  men  work  slower  than  otliers,  however,  it  is 
usual  to  estimate  at  6  hours  per  man  for  the  lifting  of  4  cu.  yds. 
of  earth  from  a  trench  3.5  to  5  ft  deep  and  throwing  the  same  a 
horizontal  distance  of  10  ft. 

When  it  is  necessary  to  throw  the  earth  more  than  12  ft  hori- 
zontally, extra  shovelers  should  be  provided  for  rehandling  it,  in 
the  proportion  of  1  shoveler  to  every  2  diggers. 

When  exposed  to  the  enemy's  fire,  a  skirmish  line  is  kept  well 
to  the  front  and  the  earth  first  excavated  is  thrown  close  to  the 
edge  of  the  ditch,  forming  a  screen  which  is  gradually  thickened; 
under  other  circumstances  the  earth  first  excavated  is  thrown 
farthest. 

Five  feet,  or  two  paces,  is  the  usual  distance  apart  for  men  to 
work,  but  they  may  be  posted  as  close  together  as  4  ft.,  while  using 
the  heavy  pick  and  shovel.  As  a  precaution  against  injury  to  ad- 
jacent workers,  the  men  should  swing  the  pick  in  a  direction  per- 
pendicular to  the  tape. 

112.— Working  parties  may  be  extended  at  less  or  greater  in- 
tervals by  making  the  corresponding  changes  in  the  commands: 
when  this  is  done,  it  will  usually  be  necessary  to  verify  intervals. 

When  necessary  to  complete  a  task  in  the  shortest  possible  time, 
or  when  the  men  available  greatly  exceed  the  number  of  tools, 
working  parties  should  be  formed  in  double  rank,  two  men  being 
assigned  to  each  set  of  tools,  which  should  be  carried  by  the  front 
rank  man.  When  working  in  this  manner  with  a  double  relief, 
the  men,  under  direction  of  non-commlssjoned  oflScers,  should 
change  off  every  10  or  15  minutes. 

Officers  having  general  supervision  of  the  work  should  not  be 
changed  at  the  same  time  the  reliefs  are. 

The  sizes  of  tasks  based  on  the  4  yd.  rule  may  be  arranged  as 
shown  in  diagram.  (Fig.  4.)  For  arrangement  of  tasks  in  difficult 
soil,  see  PI.  14. 


CHAPTER  IX.— Revetting  Materials  and 
Revetments. 

113.-  A  Revetment  is  a  facing  used  to  liold  up  an  embank- 
ment at  a  steeper  slope  tlian  it  would  assume  naturally. 

1 14.— Revetting  Materials.  Tlie  revetments  most  commonly 
used  in  field  engineering  are  made  either  of  brushwood  in  the 
rough,  fascines,  gabions,  hurdles,  planks,  timber,  sods,  sand-bags, 
pisa,  adobe,  bamboo,  or  of  a  combination  of  two  or  more  of  these. 

115.— Brushwood,  which  is  used  in  making  the  first  four, 
should  be  of  willow,  birch,  ash,  hickory,  or  hazel,  and  is  most  pli- 
ant when  not  in  leaf:  it  may  be  of  any  size  when  used  in  the  rough, 
but  should  not  exceed  an  inch  in  butt  diameter  for  gabions  and 
hurdles  and  2.5  in.  for  fascines  and  pickets. 

The  working  party  cuts  and  binds  the  brushwood  in  bundles 
of  about  40  lbs.  each,  putting  the  large  and  small  in  separate  piles 
with  butts  in  the  same  direction.  For  convenience,  the  detail 
should  be  divided  into  three  parts— one  for  cutting,  one  for  sort- 
ing and  binding,  the  other  for  carrying  and,  if  necessary,  loading. 
Tools  required  and  time  necessary  are  as  in  ''Clearing  the  Ground'* 
(Chap.  v.). 

116.— Withes  (PL  17,  Fig.  1),  which  are  used  for  binding  and 
sewing,  are  made  by  twisting  pliant  rods.  The  butt  is  held  under 
the  left  foot  and  the  twisting  commenced  at  the  small  end,  care 
being  taken  to  avoid  breaking  or  kinking  the  rod.  The  pliancy  of 
the  rod  may  be  increased  by  heating  it.  In  using  the  withes  for 
binding,  an  eye  is  made  at  the  small  end,  then  the  withe  is  passed 
round  the  bundle,  the  butt  passed  through  the  eye  and  twisted 
until  a  kink  is  formed,  when  the  butt  is  thrust  (buried)  in  the 
bundle. 

117.— Fascines.  A  fascine  is  a  bundle  of  rods  tightly  bound 
together.  It  has  a  length  of  18  ft.,  a  diameter  of  9  in.,  and  weighs 
about  140  lbs. 

Pascine  Rack.  The  fascine  is  made  In  a  cradle  rack  of  five 
equidistant  trestles  (Figs.  2  and  4),  the  outer  ones  being  16  ft. 
apart;  the  crotches  are  each  2.5  ft.  above  the  ground  and  aligned. 
The  stakes  for  the  trestles  should  be  from  2.5  to  4  in.  in  diameter 


PLATE  17 


Revetting  Materials  and  Revetments.  63 

and  from  5  to  6  ft.  in  length.  Those  for  the  outer  trestles  are  first 
driven  and  securely  bound  together  with  wire  or  rope,  then  a  line 
is  stretched  from  crotch  to  crotch  and  the  interior  trestles  made 
in  a  similar  manner;  the  stakes  should  be  driven  firmly  into  the 
ground  and  each  should  have  a  length  of  2  ft.  above  the  crotch. 

Fascine  Choker.  For  the  purpose  of  gauging  the  circum- 
ference of  the  fascine  and  for  cramping  it  in  binding,  the  fascine 
choker  (Fig.  3)  is  used.  It  consists  of  two  stout  bars  or  hand- 
spikes, 4  ft.  long,  to  each  of  which  is  attached  a  collar  18  in.  from 
the  end,  the  collars  being  connected  by  a  stout  chain,  to  which 
are  attached  two  gauge  links  28  in.  apart.  The  choker  is  used  by 
a  man  on  each  side  of  the  rack  taking  a  bar  of  it  and  resting  the 
short  end  on  top  of  the  fascine,  chain  being  underneath  (Fig.  4, 
"a");  then  each  passes  his  bar  over  to  the  other  (the  short  ends 
passing  around  and  under  the  fascine),  and  each  bears  down  on 
the  end  of  his  lever.     (Fig.  4,  "b.") 

Making  the  Fascine.  The  trestles  having  been  prepared, 
the  fascine  is  made  by  laying  brushwood,  trimmed  if  practicable, 
in  them,  the  pieces  breaking  joints  and  crooked  ones  being  partly 
sawed  or  cut  through.  The  rods  should  extend  from  18  in.  to  2  ft. 
beyond  the  extreme  trestles  and  the  bunch  made  of  uniform  size 
throughout.    (Fig.  4.) 

The  choker  should  be  used  occasionally  for  testing  the  size,  and 
when  of  such  dimensions  throughout  that  the  gauge  rings  meet, 
the  fascine  is  bound.  This  should  be  done  with  wire  or  tarred 
rope,  which  is  passed  twice  round  the  fascine  and  securely  fas- 
tened, the  bindings  being  12  in  number,  the  two  outer  ones  3  in. 
outside  the  extreme  trestles  and  the  others  at  intervals  of  about  a 
foot  and  a  half.  This  allows  the  fascine  to  be  cut  into  lengths  of 
6  or  of  9  ft.    Five  men  require  about  an  hour  to  make  a  fascine. 

118.— Gabions.  Gabions  are  open  cylinders  2  ft.  in  exterior 
diameter  by  2  ft.  9  in.  in  height,  varying  in  weight  from  35  to  50 
lbs. :  they  are  made  of  brushwood,  strap  iron,  iron  bands  or  sheet  iron 
and  from  9  to  14  pickets  each.  The  interlaced  brushwood  in  gabions 
is  called  the  watling  or  web.  Gabion  pickets  should  be  3.5  ft.  in 
length  and  from  an  inch  to  an  inch  and  a  half  in  diameter.  The 
rods  for  the  web  should  be  from  one-half  to  three-fourths  of  an 
inch  in  diameter,  although  smaller  may  be  used.    Wicker  gabions 


64  Revetting  Materials  and  Bevetments. 

are  most  easily  made  with  the  aid  of  a  gabion  form,  wliich  is  a 
circular  piece  of  board  21  iu.  iu  diameter,  with  equidistant  notches 
on  its  circumference,  the  number  of  notches  depending  on  the  size 
of  the  brushwood  and  running  from  9  to  14.    (Fig.  5.) 

The  construction  of  the  Wicker  Gabion  (Fig.  7)  is  as  follows: 
Watling.  The  gabion  form  is  laid  on  level  ground  and  a 
picket  driven  vertically  in  each  notch,  the  thick  and  thin  ends  of 
the  pickets  alternating.  The  form  is  then  slipped  up  the  pickets 
about  a  foot  and  held  firmly  in  place  by  means  of  a  rope,  which  is 
tied  loosely  round  the  pickets  just  below  the  form  and  then  tight- 
ened by  a  rack  stick  (Fig.  6),  the  rope  holding  the  pickets  firmly 
in  the  notches.  The  rods  for  the  web  having  been  stripped  of 
their  leaves,  the  web  is  commenced  by  laying  the  butts  of  two  rods 
in  adjacent  spaces  between  pickets,  resting  on  the  form.  The  rear 
rod,  passing  outside  the  second  picket,  is  then  bent  inward,  pass- 
ing over  the  first  rod,  inside  the  third  picket,  and  then  out.  (Fig. 
5.)  The  other  rod,  which  is  now  the  rear  one,  is  similarly  treated 
and  the  watling  continued  by  using  the  rods  alternately.  This 
method  of  watling  is  called  pairing.  On  coming  to  the  end  of  a 
rod  a  fresh  one  is  laid  alongside  and  woven  with  it  for  a  short  dis- 
tance. The  web  is  continued  to  within  3  in.  of  the  ends  of  the 
pickets,  care  being  taken  to  keep  the  pickets  vertical  and  to  make 
the  web  close  by  frequent  use  of  the  mallet. 

Sewing.  To  prevent  the  web  from  coming  off  the  pickets  it 
is  then  sewed  with  wire,  heavy  twine,  or  withes,  in  four  places,  as 
follows:  Take  an  end  of  a  withe  in  each  hand,  the  middle  of  it 
resting  on  top  of  the  web,  pass  the  ends  of  it  through  the  web  about 
6  in.  down  the  sides,  one  from  without  inward  and  the  other  from 
within  outward;  pull  taut  by  bearing  downward.  Pass  the  ends 
through  the  web  again  G  in.  farther  down  and  tighten  as  before. 
Proceed  in  the  same  manner  a  third  time  and  then  bury  the  ends 
of  the  withe  in  the  web.  The  sewing  should  be  at  equal  inter- 
vals and  the  two  ends  of  the  withe,  when  pushed  through  the 
web,  should  be  separated  by  two  or  three  of  the  watling  rods;  wire 
is  much  easier  worked  and  more  durable  than  withes.  The  partly 
completed  gabion  is  now  inverted,  the  form  removed,  and  the  wat- 
ling continued  as  before,  until  the  gabion  has  a  height  of  2  ft.  9  in., 
when  it  is  completed  by  again  sewing  as  before  explained.  The 
ends  of  the  pickets  that  were  driven  Into  the  ground  are  now 


Revetting  Materials  and  Revetments.  05 

trimmed  to  within  3  in.  of  tlie  web  and  sharpened,  the  opposite 
ends  sawed  off  to  within  an  inch  of  the  web,  and  a  carrying  picket 
driven  through  the  sides  of  the  gabion  perpendicular  to  the  axis 
and  a  few  inches  from  it. 

Three  men  should  make  a  gabion  in  an  hour. 

119.— Wicker  Gabion  Without  the  Gabion  Form.  Where 
the  form  is  not  at  hand,  the  wicker  gabion  is  made  by  first 
describing  on  the  ground  a  circle  with  a  10.5  in.  radius  and  then 
driving  the  pickets  at  equidistant  intervals  on  this  line.  The 
watling  is  commenced  at  the  ground  and  run  up  to  the  full  height, 
care  being  taken  by  frequent  gauging  to  keep  the  dimensions 
accurate.  It  will  be  necesary  for  one  man  to  devote  his  entire 
attention  to  keeping  the  pickets  in  position,  while  a  second  makes 
the  web,  and  a  third  prepares  the  rods.  Three  men  should 
make  a  gabion,  without  the  form,  in  an  hour  and  a  half  to  two 
hours.  Instead  of  sewing,  the  gabion  may  be  finished  by  driving 
four  forked  pickets  (Fig.  8)  in  the  web  alongside  of  the  gabion 
pickets. 

120.— The  Hoop  or  Strap  Iron  Gabion.  This  is  more  dura- 
ble and  more  quickly  made  than  the  wicker  gabion,  but  is 
heavy,  weighing  55  lbs.,  and  liable  to  splinter  dangerously.  The 
form  for  this  gabion  is  used  solely  for  gauging  and  shaping  the 
bands. 

To  make  the  hoops,  describe  on  a  wooden  platform  a  circle 
with  a  1  ft.  radius  and  divide  it  into  6  equal  parts.  Make  auger 
holes  at  points  of  division  and  insert  in  them  wooden  pins  about 
5  in.  long  and  triangular  in  cross  section,  the  bases  of  the  tri- 
angles being  on  the  interior  of  the  circle.  (Fig.  9.)  Wrap  the 
strap  iron  once  tightly  round  the  pins,  thus  forming  an  hexagonal 
hoop.  Mark  the  point  where  the  hoop  is  to  be  joined,  then  remove, 
punch,  and  rivet  it.  As  the  iron  is  usually  1  in.  wide,  the  com- 
pleted gabion  will  require  33  of  these  hoops. 

To  make  the  gabion,  place  a  hoop  on  the  ground  and  an- 
other on  it  in  the  positions  shown.  (Fig.  10.)  Drive  a  picket 
vertically  in  each  of  the  triangular  spaces,  then  place  the  remain- 
ing hoops  alternately  over  the  first  and  second.  Drive  nails  in 
four  of  the  pickets  outside  the  extreme  hoops  to  keep  the  gabion 
intact. 

121.— The  Sheet  Iron  Gabion.    This  gabion  is  made  of  a  piece 


^^  Revetting  Materials  and  Revetments. 

of  sheet  iron  2  It.  U  iu.  x  6  it.  4  in.,  riveted  or  wired  togetlier  along 
its  shorter  edges. 

122.— Hurdles.  The  hurdle  is  a  brushwood  mat  2  ft.  9  in. 
wide  by  6  ft.  long,  the  length  corresponding  very  nearly  to  the 
circumference  of  the  gabion.  An  even  number  of  pickets,  usually 
10,  is  used  in  making  it,  the  extreme  pickets  being  somewhat 
heavier  than  the  interior  ones.    (Fig.  11.) 

Construction  of  Hurdles.  Describe  on  the  ground  an  arc 
with  an  8  ft.  radius,  measure  off  6  ft.  of  this  arc  and  drive  10 
gabion  pickets  along  it  at  intervals  of  8  in.  (Fig.  11.)  Commence 
the  watling  in  the  center  space  on  the  ground  by  randing— i.  e., 
working  with  a  single  rod  alternately  inside  and  outside  of  the 
pickets;  on  reaching  the  end  picket  the  rod  should  be  twisted  as 
a  withe,  so  as  to  avoid  breaking  it,  and  then  returned  toward  the 
center  in  the  same  manner  as  at  first.  When  approaching  the 
end  of  a  rod  another  should  be  laid  alongside  of  and  randed  with 
it  for  a  distance  of  two  or  three  pickets.  Pairing,  as  in  gabions, 
should  be  resorted  to  in  finishing  the  top  and  bottom  of  the  web, 
and  the  hurdle  should  then  be  sewed  as  described  for  the  gabion. 
When  the  rods  used  in  watling  are  very  small  the  process  of  slew- 
ing should  be  resorted  to:  this  is  the  same  as  randing  with  the 
exception  that  2  or  3  rods  are  laid  alongside  each  other  instead  of 
using  them  singly.  Slewing  makes  weaker  work  than  randing. 
Three  men  should  make  a  hurdle  in  two  hours;  two  work  at  the 
web  and  the  third  prepares  the  rods.  The  completed  hurdle 
weighs  about  50  lbs.  The  hurdle  is  made  on  a  curve  and  after- 
ward flattened  as  much  as  possible,  because  it  is  found  that  by 
so  doing  it  is  less  liable  to  warp  than  if  made  flat.  It  should  be 
placed  in  a  road  or  revetment  with  the  concave  side  toward  the 
earth. 

123.— The  Continuous  Hurdle  is  usually  preferred  for  revet- 
ting purposes  to  single  ones  joined.  It  differs  from  the  latter 
in  that  the  pickets  are  driven  at  once,  at  intervals  of  12  to  18  in. 
according  to  their  thickness,  in  the  position  the  revetment  is  to 
occupy,  but  at  a  slightly  gentler  slope,  so  as  to  allow  for  straight- 
ening when  the  earth  is  tamped.  It  is  constructed  by  randing  or 
slewing,  two  men  being  assigned  a  task  of  10  or  12  ft.  in  length, 
which  they  should  finish  to  a  height  of  4  ft.  and  anchor,  in  from 
one-half  to  three-quarters  of  an  hour. 


PLATE  18. 


Revetments. 


Figure  3. 


Figure  4. 


68  Revetting  Materials  and  Revetments. 

124.— Planks,  when  used  for  revetting,  should  be  placed 
edgewise  and  held  in  position  by  stout  stakes,  which  should  be 
anchored.  They  make  a  neat,  durable  and  quickly  made  revet- 
ment. 

125.— Round  timber  from  3  to  8  in.  in  diameter  may  be  used 
in  the  same  manner  as  planks,  but  the  revetment  is  more  diflScult 
of  construction  and  is  not  so  durable. 

126.— Sod  for  revetting  purposes  is  cut  of  a  uniform  size— 18 
in.  long,  9  in.  wide,  and  4  in.  thick.  They  should  be  laid  in  alter- 
nate rows  of  headers  and  stretchers,  grass  down,  breaking  joints, 
and  perpendicular  to  the  slope.  The  top  layer  should  be  all  head- 
ers and  have  the  grass  up;  alternate  rows  should  be  pinned  secure- 
ly, using  split  pickets,  if  possible,  as  with  them  there  is  less  liabil- 
ity of  splitting  the  sod  than  when  round  ones  are  used.  Two  men 
should  lay  from  70  to  100  sods  per  hour,  depending  upon  whether 
or  not  pickets  are  used. 

127.— Sand-bags  are  made  of  coarse  canvas  or  bagging 
material,  and,  when  empty,  measure  2  ft.  8  in.  by  1  ft.  4  in.  When 
filled  they  are  supposed  to  contain  1  cubic  ft.  of  earth;  it  is  found 
in  practice,  however,  that  a  cubic  yard  will  fill  from  48  to  50,  mak- 
ing their  average  size  1  ft.  6  in.  long,  10  in.  wide,  and  6  in.  thick. 
Each  bag  has  eyelet  holes  near  the  mouth  through  which  a  stout 
cord  passes,  to  expedite  tying,  when  filled. 

For  filling  sand-bags  the  working  party  is  divided  into  squads 
of  6:  2  with  shovels,  1  with  a  pick,  1  to  hold  the  bag,  and  2  to  tie. 

Each  squad  fills  150  bags  per  hour.  This  task  may  be  consid- 
erably increased,  however,  in  easy  soil  or  with  trained  men,  and 
the  rapidity  of  the  work  more  than  doubled  by  having  a  double 
relief  and  keeping  the  men  constantly  changing. 

128.— Revetments.  Brushwood  Revetment  is  made  by  driv- 
ing pickets  at  intervals  of  about  12  in.  along  the  foot  of  the 
proposed  slope.  The  top  of  the  pickets  when  driven  should  be 
as  high  as  the  proposed  revetment,  and  the  pickets  should  be 
anchored  by  wire  to  logs  or  stout  stakes  in  the  parapet.  Loose 
brushwood  is  laid  closely  behind  the  stakes  and  earth  tamped 
against  it,  the  construction  of  the  parapet  going  on  at  the  same 
time. 

Brushwood  revetment  is  rapidly  made  in  daylight,  but  is  neither 
durable  nor  sightly. 


Revetting  Materials  and  Revetments.  69 

129.— The  Fascine  Revetment.  (PI.  18,  Fig.  1.)  This  is 
made  by  laying  the  fascines  in  single  rows  of  stretchers,  breaking 
joints,  each  fascine  being  pinned  to  the  parapet  by  5  or  6  pickets, 
and  every  second  or  third  row  securely  anchored. 

Six-foot  fascines  should  be  used  occasionally  as  headers.  The 
bottom  fascine  is  sunk  about  one-third  of  its  diameter  by  excavat- 
ing a  shallow  trench.  The  construction  of  parapet  and  revetment 
proceed  simultaneously.  Slope  should  not  be  greater  than  four 
on  one.  The  defects  of  this  revetment  are  the  weight  of  the  fas- 
cines, the  large  quantity  of  brushwood  required,  and  the  fact  that 
the  fascines  are  held  in  place  by  anchors  and  pickets  in  the  earth 
which  they  support. 

130.— The  Gabion  Revetment.  (Fig.  2.)  This  is  made  by 
first  sinking  a  row  of  fascines  about  3  in.  at  the  foot  of  the  slope, 
so  as  to  give  an  inclination  of  four  on  one  to  the  gabions  resting 
partially  on  them.  Earth  is  tamped  behind  and  in  the  gabions, 
and  sod  or  sand-bags  placed  on  top.  Where  greater  height  is 
required  two  rows  of  gabions  may  be  used  with  two  fascines,  well 
picketed,  between  them. 

Gabions  make  one  of  the  strongest  and  most  durable  revet- 
ments, their  own  weight  when  filled  being  usually  sufficient  to 
retain  the  embankment. 

131.— Hurdles.  These  make  a  poor  revetment  unless  the 
method  is  followed  of  constructing  a  "continuous  hurdle''  at  the 
same  time  with  the  parapet.  To  do  this,  the  pickets  are  driven 
along  the  foot  of  the  slope  at  an  inclination  of  about  three  on  one, 
when  the  final  slope  is  to  be  four  on  one.  The  watling  is  made 
continuous  by  randing  or  slewing,  each  two  men  having  four 
paces  of  hurdle  as  a  task,  and  taking  care  to  work  in  their  rods 
with  those  of  adjacent  sections.    (Fig.  3.) 

132.— Plank  or  Timber  Revetment.  (Fig.  4.)  This  is  made 
by  driving  heavy  stakes  into  the  ground  at  the  proper  angle,  plac- 
ing the  planks  or  timbers  behind  them,  then  filling  in  and  tamp- 
ing firmly.  The  stakes  must  be  anchored.  This  revetment  Is 
neat  and  durable. 

133.— Sod  Revetment.  (Fig.  5.)  This  is  made  by  laying  the 
sod  in  alternate  layers  of  headers  and  stretchers,  grassy  side  down, 
breaking  joints  and  perpendicular  to  the  face  of  the  revetment. 


70  Revetting  Materials  and  Revetments, 

Each  sod  should  be  well  settled  before  another  is  placed  on  it  and 
the  top  laj^er  should  be  headers  with  grass  up.  It  is  well  to 
pin  alternate  rows  by  means  of  split  pickets,  three-fourths  of  an 
inch  in  diameter  and  9  in.  long.  This  revetment  is  made  of  uni- 
form thickness  throughout  by  using  double  rows  of  stretchers. 
If  the  grass  is  long  it  should  be  mowed.  If  the  sod  is  very  wet 
when  laid  the  revetment  will  crack  in  drjung.  Two  men  well 
supplied  with  sod  should  lay  two  paces  of  revetment,  four  and 
one-third  feet  high,  in  an  hour. 

This  revetment  has  the  advantage  of  not  splintering  like 
gabions,  fascines  and  boards,  but  should  not  be  used  when  other 
material  is  obtainable,  because  ordinarily  it  will  not  stand  long 
at  a  steep  slope  (three  on  one  being  about  the  Itniit),  cannot  be 
used  when  very  dry  or  frozen,  and  requires  great  care  to  build 
properly. 

134.— Sand-bag  Revetment.  (Fig.  6.)  This  is  made  by  lay- 
ing alternate  rows  of  headers  and  stretchers,  breaking  joints,  and 
perpendicular  to  slope,  seams  of  stretchers  and  chokes  of  headers 
.being  put  in  the  embankment.  Men  working  in  pairs  lay  the 
bags,  settling  them  firmly  in  place  with  a  mallet  or  spade.  This 
revetment  is  not  very  durable,  but  the  bags  are  easily  transported, 
may  be  used  with  any  soil,  and  are  invaluable  in  making  hasty 
repairs  and  loop-holes. 

135.— A  very  durable  revetment  (Fig.  7),  much  used  in  the 
defenses  of  Washington,  1861-5,  was  made  of  posts  (oak,  chestnut, 
or  cedar)  cut  in  lengths  of  5.5  ft.  and  placed  side  by  side,  at  a  slope 
of  six  on  one.  The  footing  was  a  2  in.  plank  laid  in  a  trench  exca- 
vated for  the  purpose.  The  tops  of  the  posts  were  sawed  off  16 
in.  below  the  interior  crest  and  capped  by  a  half-round  timber, 
all  being  securely  anchored  in  the  parapet.  Crowning  was  com- 
pleted to  the  requisite  height  with  sod. 

All  revetments  that  are  liable  to  splinter  should  be  crowned  to 
a  height  of  at  least  8  in.  with  sods,  sand-bags  or  earth. 

136.— Pisa  Revetment  is  made  of  earth  and  clay,  to  which 
has  been  added  enough  water  to  reduce  the  mixture  to  a  working 
consistency.  A  trench  6  in.  deep  and  18  in.  wide  is  first  dug,  its 
nearest  edge  marking  the  foot  of  the  revetment.  Pickets,  of 
suflficient  length  to  reach  the  top  of  the  proposed  revetment,  are 


Revetting  Materials  and  Revetments, 


71 


firmly  driven,  at  the  proper  angle,  about  2  in.  from  the  near  edge 
of  the  trench,  at  intervals  of  about  a  yard,  and  then  anchored. 
Boards  placed  on  edge  are  now  laid  against  the  pickets  on 
the  trench  side.  The  trench  is  then  filled  with  the  mixture, 
tamped,  and  more  added,  other  boards  being  placed  on  top  of  the 
first,  as  required,  and  the  mixture  forced  closely  against  them. 
The  construction  of  the  parapet  goes  on  at  the  same  time  with 
the  revetment.  When  completed,  the  pickets  and  boards  are 
removed.  This  revetment  is  neat  and  durable,  but  cannot  be 
rapidly  made. 

137. — Adobe  Revetment.  The  adobe  is  a  sun-dried  brick, 
about  IS  in.  X  9  in.  x  4.5  in.,  and  when  carefully  laid  with  the  same 
bond  as  given  for  sod  or  sand-bag,  forms  a  neat  and  very  durable 
revetment,  exceeding  in  the  latter  respect  any  of  the  other  varieties 
mentioned. 

137a. — Bamboo  Revetment.  Where  material  is  available  green 
bamboo  split  into  strips  an  inch  and  a  half  wide  makes  an  excel- 
lent revetment.  It  is  constructed  by  randing  in  the  same  manner 
as  the  "continuous  hurdle,"  care  being  taken  to  have  the  adjacent 
strips  break  joints. 

The  following  table  shows  amount  of  various  materials  re- 
quired for  300  running  feet  of  4  ft.  4  in.  high  revetment: 


Kind  of  Revetment 

Fascines 

Gabions 

Sod 

Sand-bags 

Pickets 

Fascines   

Gabion 

Sod 

Sand-bag   

30 
6 

50 

267 

400 

1867 

867 

150 
1000 

PLATE  19. 


Field  Casemates. 


CHAPTER  X.— Field  Casemates  and  Magazines. 

138.— In  all  field  works,  protection  against  both  weatlier  and 
liostile  fire  must  be  provided  for  the  garrison. 

These  shelters  are  constructed  by  building  a  chamber  of  wood 
sufficiently  strong  to  bear  the  necessary  earth  covering,  and  by 
protecting  this  in  front  by  an  embankment  thick  enough  to  with- 
stand direct  artillery  fire. 

Two  general  forms  are  used: 

(1)  Those  which,  after  providing  complete  protection  from 
direct  fire,  have  their  roofs  sloped  to  the  rear  at  an  angle  greater 
than  the  angle  of  descent  of  the  enemy's  projectiles,  generally 
about  one  on  four;  and 

(2)  Those  which  have  horizontal  roofs,  the  earth  covering  being 
so  high  and  massive  as  to  protect  against  artillery  fire  by  its  thick- 
ness alone. 

The  first  class  is  preferable,  the  work  of  construction  being  very 
much  less  than  in  the  second  class,  as  the  embankment  is  not  so 
high  and  the  earth  on  the  roof  does  not  require  to  be  thicker  than 
16  in.,  as  it  has  to  resist  only  the  dropping  fire  of  small-arms  and 
the  fragments  from  bursting  shrapnel.  Moreover,  it  gives  much 
easier  drainage  to  the  ditch  in  rear. 

139.— The  construction  of  the  timber  part  of  the  casemate  is 
practically  the  same  in  both  cases.  The  vertical  timbers  being 
rough  tree  trunks,  about  1  ft.  in  diameter,  placed  at  intervals  of 
3  or  4  ft.,  and  strutted  when  necessary.  The  roof  timbers  in  sim- 
ple casemates  being  not  less  than  8  in.  in  diameter  and  the  inter- 
stices filled  with  small  poles  or  brush.  In  case  the  protection  has 
to  be  proof  against  vertical  fire  of  mortars,  the  earth  mask  on  the 
roof  must  be  6  ft.  in  thickness  and  a  correspondingly  stronger 
timber  construction  must  be  provided:  these  are  shown  in  PI.  19, 
Figs.  1  to  7. 

In  calculating  floor  space,  each  man  should  have  from  9  to  18 
sq.  ft.;  the  former  when  crowded,  the  latter  when  not. 

139a. — The  following  Is  a  bomb-proof  construction  which  would 
be  safe  under  the  fire  of  projectiles  having  a  bursting  charge  of 
9.9  pounds  of  explosive  gelatine  and  a  penetration  of  5  feet  before 
bursting: 


74  Field  Casemates  and  Magazines. 

1.  Frames  of  8-by-8-inch  pine,  5.5  feet  high  and  6.5  feet  wide 
in  the  clear,  with  upper  corners  braced,  spaced  10  inches  apart. 

2.  Sides  of  poles  or  botards  outside  the  frames. 

3.  On  top:  (a J  a  longitudinal  layer  of  double  thickness  of  rail- 
road iron  or  a  double  thickness  of  4-by-6-inch  timbers;  (h)  cross 
layer  of  fascines;  (cj  longitudinal  layer  of  8-by-8-inch  oak;  (dj  9 
feet  of  earth;  (ej  20  feet  of  earth  on  exposed  side. 

140.— Magazines  are  of  two  kinds:  First,  those  intended  to 
hold  the  temporary  supply  for  guns  or  troops  when  in  action;  and. 
Second,  those  intended  for  the  purpose  of  storing  ammunition  in 
large  quantities. 

The  first  variety  consists  of  recesses  in  the  interior  slope  of  the 
epaulement— barrels  or  gabions  are  excellent  and  when  not  obtain- 
able may  be  replaced  by  empty  ammunition  boxes  placed  in  holes 
excavated  for  their  reception. 

Magazines  of  the  second  class  are  used  only  in  works  of  great 
defensive  value  and  then  only  when  ample  time  is  available. 
They  are  made  in  the  same  general  manner  as  the  casemates 
heretofore  described,  except  that  great  care  must  be  taken  to 
render  the  structure  as  dry  as  possible  and  to  secure  good  venti- 
lation. 

141.— The  general  plan  of  execution  of  these  works  is  as 
follows:— 

(1)  Magazine  shown  in  PI.  20,  Fig.  1. 

The  mask  in  front  should  be  20  ft.  thick.  The  roof  consists  of 
a  row  of  timbers  or  logs  8  in.  in  diameter,  overlaid  with  steel  rails, 
and  then  covered  with  a  paulin,  well  tarred  if  possible.  On  this 
is  placed  16  to  18  in.  of  earth.  The  ends  are  made  of  logs,  12  in. 
in  diameter,  planted  in  a  double  row,  Breaking  joints.  The  en- 
trance is  at  either  one  or  both  ends  according  to  circumstances. 
The  doors,  2  ft.  6  in.  in  width,  are  made  of  planks  crossed,  and  are 
hung  next  to  the  front  wall  of  trench,  opening  into  a  passage 
formed  by  a  row  of  upright  logs  parallel  to  those  on  the  end  of 
the  magazine.  At  the  end  of  the  passage  farthest  from  the  first 
door  a  second  one  is  hung,  opening  into  the  magazine.  The  ver- 
tical timbers  in  front  and  rear  of  trench  support  a  revetment  of 
planks  or  hurdles.  The  floor  should  be  raised  at  least  6  in.  from 
the  bottom  of  the  trench  to  guard  against  dampness.  Care  should 
be  taken  to  facilitate  the  draining  of  all  water  that  falls  on  the 


PLATE  20. 


]\I^agazine  behind  naranet. 


Tu/o  S'tortecl  Block HousQ, 

Ca/ionier  in  front  ofwalL 


7(5  Field  Casemates  and  Magazines. 

roof,  and  that  the  trench  itself  is  drained  away  from  the  ends  of 
the  magazine. 

142.— Another  form  is  as  follows:— Determine  the  space  need- 
ed for  storage  of  ammunition.  Then  build  the  timber  work  as 
in  the  preceding,  first  excavating  to  a  depth  of  4  or  5  ft.  over 
the  entire  site.  There  will  be  no  ends  to  be  closed  by  timbers. 
The  roof  is  made  of  timbers  12  in.  in  diameter,  well  supported  by 
uprights  of  sam<)  size  and  long  enough  to  give  sufficient  head 
room.  The  sides  and  ends  should  be  revetted  with  planli,  if  pos- 
sible, and  the  floor  raised  6  in.  above  the  earth.  The  center  of 
the  roof  is  raised  a  foot  above  the  sides  and  surmounted  by  a 
layer  of  6  in.  of  earth,  well  tamped;  over  this  is  laid  a  paulin  and 
the  earth  mask  is  then  placed  over  all  to  the  thickness  of  8  ft.; 
the  covering  mass  in  front  should  not  be  less  than  20  ft.  in  thick- 
ness. Entrance  is  gained  by  means  of  a  doorway  opening  into 
a  passage  which  communicates  through  a  return  with  the  inte- 
rior of  the  magazine.  Doors  made  of  crossed  planks  are  hung 
as  indicated  in  the  plan.  If  time  is  available,  and  the  planks 
at  hand,  an  interior  chamber  should  be  formed,  leaving  an  air 
space  around  the  magazine  proper;  and  inlets  may  be  constructed, 
care  being  taken  that  they  are  not  situated  in  exposed  positions 
and  that  their  course  is  such  as  to  prevent  the  entrance  of  sparks. 
The  roof  should  be  rounded  off  so  as  to  afford  the  easiest  drain- 
age. If  the  earth  excavated  is  not  sufficient  to  cover  the  roof, 
the  necessary  amount  may  be  taken  from  a  trench  dug  around  the 
outside. 

This  form  of  magazine  may  with  advantage  be  placed  in  a 
traverse. 

143.— In  case  timber  is  not  at  hand,  gabions  and  fascines  may 
be  used  to  build  the  magazine  in  the  manner  shown  In  PI.  20. 

144.— Block  Houses  are  defensible  shelters  for  infantry,  al- 
though, under  certain  circumstances,  they  contain  artillery. 

They  are  generally  used  for  the  purpose  of  flanking  defenses 
whose  fire  cannot  reach  into  the  ditch. 

They  are  constructed  either  of  upright  timbers  set  in  the  ground 
close  together,  or  horizontal  timbers  laid  one  upon  the  other;  the 
timbers  being  in  two  rows,  breaking  joints  in  each  case,  or,  if  both 
methods  are  used,  the  outside  row  should  be  horizontal  and  the 


Field  Casemates  and  Magazines.  11 

iuuer  vertical.  They  should  have  at  least  6  ft.  of  head  room  and 
should  not  be  less  than  9  ft.  wide,  as  this  allows  one  row  of  beds 
only.  The  roof  should  be  of  solid  construction  and  covered  with 
earth  to  the  thickness  of  2  ft.  and  should  project  2  ft.  over  the 
wall  to  protect  from  dropping  fire. 

The  walls  should  be  masked  with  earth  as  high  as  possible  and 
a  ditch  dug  around  the  entire  building.  Loop-holes  are  made  at 
the  height  of  4  ft.  4  in.  and  are  cut  according  to  circumstances, 
as  described  in  Chap.  XIII.  If  necessary,  block  houses  may  be 
sunk  in  the  ground,  but  a  limit  of  4  ft.  in  depth  should  be  observed. 
The  shape  will  conform  to  the  necessities  of  the  case. 

145a. — The  Spanish  Block  House  is  a  modified  form  of  the 
one  d^escribed;  it  is  loopholed  for  two  or  three  tiers  of  fire,  and 
as  asecondary  defense  of  especial  value  if  attacked  by  artillery, 
it  has  shelter  trenches  far  enough  in  front  to  escape  splinters  from 
the  house.     (See  Par.  191.) 

145.— In  isolated  positions  they  are  advantageously  made 
cruciform,  thus  presenting  an  opportunity  for  flanking  each  face 
of  the  house.  When  in  wooded  and  mountainous  countries, 
where  artillery  is  not  to  be  feared,  these  houses  may  be  made  with 
two  stories,  built  so  that  the  angles  of  the  upper  story  project  over 
the  sides  of  the  other,  forming  a  machicoulis  gallery,  thus  prevent- 
ing the  occupation  by  the  enemy  of  the  dead  space  in  front  of 
the  straight  walls. 

146. — Caponiers  are  sunken  block  houses  placed  in  the  ditch 
of  fortified  places  to  prevent  their  occupation  by  the  enemy:  they 
are  loop-holed  about  18  in.  from  the  ground,  so  as  to  have  the  most 
effective  plane  of  fire.    (PI.  20.) 

147.— Tambours  are  essentially  block  houses,  having  for  their 
object  the  protection  of  angles,  and  the  flanking  of  sides  of  build- 
ings, and  are  especially  useful  in  defending  doors  of  buildings. 


CHAPTER  XI.— Field  Works  in  Combination. 

148.— Where  several  field  works  are  used  in  conjunction,  either 
as  an  intrenched  position  or  in  the  investment  of  a  fortress,  city, 
or  other  important  point,  they  constitute  what  is  linown  as  a  Line 
of  Works. 

A  Line  of  Works  may  be  continuous,  that  is,  forming,  together 
with  natural  obstacles,  an  unbroken  line,  or,  with  intervals,  by 
which  it  is  understood  that  the  works  are  distinct,  either  support- 
ing each  other  or  not,  and  the  spaces  between  them  not  impassable 
by  reason  of  natural  obstacles. 

149.— Lines  with  intervals  have  the  following  advantages  over 
continuous  UneSt  viz.  :— 

(a)  They  involve  less  labor. 

(b)  The  garrison  of  the  defenders  may  be  smaller. 

(c)  They  allow  greater  freedom  of  movement  for  counter- 
attacks. 

The  general  principle  to  be  followed  in  their  construction  con- 
sists in  forming  a  line  of  fortified  points  or  pivots.  These  points 
or  pivots  detain  the  enemy's  advance,  since  he  would  hardly  pass 
them  and  expose  his  flanks  and  rear,  while  a  continued  unsuccess- 
ful attack  on  the  strongly  fortified  pivots  would  open  the  way  for  a 
counter-attack  by  the  defenders. 

When,  however,  the  defense  is  intended  to  be  solely  passive, 
which  would  be  the  case  while  awaiting  reinforcements,  or  when 
the  enemy  greatly  outnumbers  the  defenders,  the  intervals  would 
be  obstructed  by  felling  trees  or  using  any  available  obstacles, 
since  counter-attack  is  not  contemplated. 

In  the  use  of  lines  with  intervals,  if  the  general  defensive  line 
is  straight  the  works  could  be  blunted  lunettes  with  flanks  traced 
so  as  to  protect  the  front  of  adjacent  works.  If  on  a  convex  curve, 
the  capitals  should  radiate  from  a  common  center,  while  on  a  curve 
concave  toward  the  enemy,  the  capitals  should  converge  and  the 
front  of  each  work  might  be  a  straight  line. 

When  impracticable  to  construct  the  main  works  of  a  line  with 
intervals,  within  supporting  distance  (600  yds.  for  infantry  and 
2000  yds.  for  artillery)*  of  each  other,  intermediate  works  retired 


♦Continuous  dangerous  space  for  Springfield  Magazine  rifle  is  about  600  yds. 


Field  Works  m  Comhination.  79 

from  the  main  line,  not  more  than  half  the  interval,  may  be 
used. 

In  PI.  21,  Fig.  6,  is  shown  such  an  arrangement,  the  pivots  being 
single  works  while  the  artillery  is  retired  from  the  main  line  and 
supported  by  infantry  in  shelter  trenches. 

Where  the  interval  is  as  great  as  1500  yds.  it  is  advisable  to 
strengthen  the  pivots  considerably,  forming  groups,  the  individ- 
ual works  of  each  group  being  so  traced  as  to  afford  mutual  de- 
fense. (PI.  15,  Fig.  2.)  Each  group  in  this  latter  arrangement 
forms  a  strongly  fortified  point  of  support  and  would  usually  have 
sufiicient  strength  in  itself  to  resist  assault. 

150.— Sometimes,  when  the  defense  of  a  line  is  of  vital  import- 
ance to  the  defenders,  a  double  line  of  works  is  employed,  the  front 
line  being  shelter  trenches  or  open  field  works  of  slight  profile, 
the  second  line,  not  over  500  yds.  in  rear  of  the  first,  being  field 
works  of  strong  profile. 

151.— Artillery  should,  as  a  rule,  be  placed  outside  of  and  some- 
what retired  from  the  works  and  protected  by  their  own  gun-pits 
or  epaulements,  for  the  reasons— 

(1)  That  the  works  gain  much  in  simplicity  and  rapidity  of 
construction. 

(2)  That  this  disposition  draws  the  enemy's  artillery  fire  from 
the  works  and  renders  it  more  scattering. 

(3)  Greater  mobility  is  given  to  the  defender's  artillery  in  case 
of  advance  or  retreat. 

(4)  A  better  tactical  position  for  this  arm  can  often  be  secured 
than  the  one  selected  for  infantry. 

152.— As  examples  of  continuous  lines,  PI.  21,  Fig.  1,  is  known 
as  the  redan  trace  with  curtains.  Fig.  2  is  a  modification  of  Fig. 
1,  the  redans  being  blunted.  Fig.  3  is  the  tenaille  trace.  Fig.  4 
is  a  tenaille  and  redan  trace.  The  cr^maillere  trace  (Fig.  5)  has 
long  faces  and  short  flanks. 

With  respect  to  the  continuous  lines  above  mentioned,  the 
preference  on  a  level  site  would  usually  be  given  to  the  trace  shown 
in  Pigs.  1  and  2,  the  artillery  being  placed  in  the  most  favorable 
position  along  the  curtains,  with  machine  guns  in  the  most  im- 
portant redans. 

The  tenaille  and  the  tenaille  and  redan  trace  (Figs.  3  and  4) 
-6- 


PLATE  21. 


riG.l. 


FIG.2. 


FIG.5. 


(^^^^  ^%       FIG,6.  ^t  ^ 


Field  Works  in  Gomhmation,  81 

are  objectionable,  in  that  they  involve  more  labor,  cannot  bring  as 
direct  a  fire  to  the  front,  and  the  faces  are  liable  to  enfilade  when 
the  salient  angles  approach  90°,  while  on  the  other  hand,  if  a 
salient,  as  "S,"  Fig.  4,  approaches  120°,  mutual  defense  of  the 
faces,  *'f"  and  "g,"  would  be  lacking,  thus  making  the  redan,  "R," 
necessary.  This  trace  may,  however,  be  rendered  unavoidable  by 
the  conformation  of  the  ground. 

The  cr6maillere  trace  finds  special  application  in  a  position  such 
as  is  indicated  in  Fig.  5,  viz.,  joining  two  points,  one  at  the  top  and 
the  other  at  the  bottom  of  a  slope,  the  short  flanks  affording  but 
limited  opportunity  for  enfilade  fire. 

153.— The  strength  of  a  defensive  position  lies  in  a  great 
measure  in  the  proper  utilization  of  the  accidents  of  the  ground; 
thus,  the  traces  that  have  been  mentioned  may  have  to  undergo 
considerable  modification  to  be  appropriate  to  the  varieties  of 
terrain  constantly  met.  It  is  evident  that,  in  a  broken  or  hilly 
country,  one  by  preference  would  occupy  the  heights.  These,  from 
a  tactical  point  of  view,  possess  the  advantage  of  overlooking 
the  low  ground  in  front,  besides  the  great  advantage  of  conceal- 
ing from  the  enemy  the  movements  of  our  own  troops  in  rear;  but, 
since  all  else  must  be  subordinated  to  fire  effect,  it  is  evident  that 
such  a  line  on  the  heights  should  be  selected  that  the  defenders 
may  completely  cover  the  ground  over  which  the  enemy  must 
approach.  This  naturally  leads  to  the  inquiry  as  to  how  that  line 
may  be  determined. 

Heights,  great  or  small,  usually  present  the  profile  shown 
in  Fig.  7,  that  is  to  say,  they  have  a  steepest  slope,  "b  c,"  which 
is  joined  to  the  crest  and  to  the  valley  below  by  the  two  gentler 
slopes,  "a  b"  and  *'c  d."  In  order,  then,  to  beat  the  zone  "b  c"  it 
is  necessary  to  occupy  the  crest  "c"  or  some  point  below  it  on  this 
slope.  To  distinguish  this  crest  from  others,  it  will  be  called  the 
military  crest. 

With  the  Inclination  of  this  steepest  slope  greater  than  one  on 
four,  it  is  unusual  to  construct  anything  but  shelter  trenches 
along  the  military  crest,  the  artillery  being  retired  sufficiently  and 
placed  in  such  positions  as  to  command  a  good  view  of  the  rest  of 
the  field.  With  gentler  slopes,  however,  the  artillery  may  be 
placed  at  intervals  along  the  military  crest,  the  intermediate  spaces 
being  held  by  infantry  in  shelter  trenches. 


82  Field  Works  in  Combination. 

A  better  disposition  than  this,  where  the  ground  permits  of  it, 
is  to  place  the  infantry  trenches  part  way  down  the  slope  in  front 
of  the  militai-y  crest,  the  artillery  occupying  a  position  in  rear  of 
and  close  to  the  crest,  so  that  little  more  than  the  muzzles  of  the 
pieces  are  visible.  In  this  case,  care  must  be  taken  that  the  infant- 
ry* trenches  do  not  mask  the  fire  of  the  artillery. 

In  choosing  a  defensive  position  the  ground  should  be  viewed 
from  the  highest  point  in  the  vicinity,  and  by  frequent  practice  the 
eye  so  trained  that  the  military  crest  is  at  once  apparent  and  the 
slopes  instinctively  classified  with  respect  to  their  use  by  the 
different  arms. 

Finally,  the  distance  to  a  number  of  visible  permanent  points 
in  front  of  the  works  should  be  determined  and  recorded,  so  that 
there  may  be  no  necessity  for  range  finding  during  the  enemy's 
advance. 


PLATB  22. 


WigA 


v^#      Fi^.2. 


Fie  3 


WiSi4, 


CHAPTER  XII.— Siege  Works. 

154.— When  it  becomes  necessary  to  besiege  a  place,  it  may  be 
approached  by  common  trench  worli  or  by  some  form  of  sapping. 
As  the  common  trench  and  the  flying  sap  are  the  work  of  Infantry, 
they  alone  will  be  referred  to. 

155.— The  method  of  providing  the  working  party  with  tools, 
laying  out  the  work,  and  extending  the  working  party  is  described 
in  Chap.  VIII.  It  is  to  be  noted,  however,  in  work  of  this  char- 
acter, thai  ichen  extending  along  a  zig-zag,  upon  reaching  the  angle 
the  order  of  forming  up  must  he  reversed.  Thus,  if  the  column  from 
b  to  c  (PI.  22,  Fig.  1)  were  forming  on  the  left,  upon  reaching  e  f, 
it  would  form  on  the  right. 

156.— Common  Trench  Work.  This  may  be  used  as  a  par- 
allel, an  oblique  approach,  or  communication.  The  work  done 
by  reliefs  in  constructing  a  parallel  is  shown  in  Fig.  2.  In  this 
case,  as  musketry  fire  must  be  provided  for,  the  second  relief  cuts 
out  the  top  step.  Should  it  be  necessary  to  revet  the  bottom  step, 
fascines  for  this  purpose  may  be  carried  by  the  second  and  third 
reliefs.  This  may  be  and  usually  is  omitted  until  the  parallel  is 
completed.  Fig.  3  shows  the  common  trench  used  as  an  oblique 
approach  or  communication.  Should  the  trench  be  found  wide 
enough  the  task  of  the  third  relief  may  be  omitted. 

157.— The  Flying  Sap  (Fig.  4)  is  similar  to  common  trench 
work,  except  that  in  the  former  case  the  embankment  is  revetted 
with  gabions. 

In  taking  tools,  each  man  of  the  first  relief  is,  in  addition  to  his 
pick  and  shovel,  provided  with  two  gabions.  In  laying  out  the 
tools,  a  shovel  should  be  fastened  in  one  gabion  by  being  placed 
between  tAvo  of  the  gabion  pickets,  handle  of  the  shovel  inside. 
A  pick  should  be  secured  in  the  other  gabion  by  having  its  point 
pushed  under  the  pairing  rods,  handle  Inside.  The  gabion  with 
shovel  is  taken  in  the  right  hand,  the  one  with  pick  in  the  left: 
both  gabions  being  carried  by  carrying  pickets. 

158.— The  extension  in  the  flying  sap  is  made  from  single 
r^nk  on  the  right  or  left,  and  differs  from  the  extension  In  com- 


Siege  Works.  85 

mon  trench  work  in  that  the  interval,  in  the  former  case,  is  the 
width  of  two  gabions.  Each  man,  on  coming  into  line,  place© 
his  gabions  so  that  they  touch  each  other  along  the  inner  edge  of 
the  tape,  takes  out  his  tools  and  lays  them  down,  as  explained  for 
working  parties  in  Chap.  VIII.,  and  waits  for  the  command,  *'Com- 
mence  work."  In  commencing  work,  the  gabions  should  first  be 
filled;  hence  the  position  of  each  pair  of  gabions  should  be  recti- 
fied before  this  command  is  given. 

159. — Each  branch  of  a  zig-zag  should  receive  such  direction 
as  not  to  expose  it  to  enfilade  fire  from  any  point  of  the  defenses. 
Its  prolongation  should,  therefore,  fall  outside  of  the  most  ad- 
vanced salient  of  the  collateral  works.  Ordinarily  it  would  not 
be  longer  than  100  yds.  A  parallel  should  be  stepped  in  order  to 
facilitate  an  advance  from  it. 

160.— A  portion  of  the  parallels  and  approaches  used  in  the 
capture  of  Fort  Wagner,  Morris  Island,  S.  C,  September  7th,  1863, 
is  shown  in  PI.  23. 


PLATE  23. 


TLATE  24. 


Figure  1 


CHAPTEB  XIII.— Defense  of  Localities. 

161.— Walls.  Should  the  enemy  close  on  them,  walls  must  be 
so  prepared  that  they  will  neither  screen  nor  cover  him,  nor  per- 
mit his  firing  from  them.  To  prevent  this,  obstacles  may  be 
placed  in  front,  or  a  ditch  may  be  dug  outside  which  will  place  him 
so  far  below  the  top  of  the  wall  or  the  bottom  of  the  loop-holes 
that  he  cannot  fire  over  the  one  or  through  the  other.  A  total 
height  of  G  ft.  will  prevent  this,  or,  in  case  of  loop-holes  close  to 
the  ground,  the  maximum  height  should  not  be  greater  than  1  ft. 
from  the  outside,  or  an  embankment  made  in  rear  18  in.  high. 

Notwithstanding  these  precautions,  walls  may  still  give  cover; 
hence  they  should  be  flanked  when  possible. 

162.~In  preparing  walls  for  defense,  the  following  cases 
arise:— 

(1)  A  wall  less  than  4  ft.  high.  Sink  a  small  trench  on  the  In- 
side to  gain  additional  cover.  Fire  over  the  top.  (PI.  24,  Fig.  1.) 
Head  cover  should  be  provided  with  logs,  sand-bags,  or  sods,  sand- 
bags being  the  best,  sods  next. 

Additional  protection  against  artillery  may  be  obtained  by  heap- 
ing earth  from  the  ditch  In  front  against  the  wall,  the  thickness 
depending  on  the  kind  of  artillery  the  wall  Is  to  resist. 

If  this  should  be  done,  the  ditch  should  not  be  too  close  to  the 
wall.  A  trench  should  be  dug  In  rear  to  give  cover  to  the  supports, 
or  for  the  firing  line  when  not  firing  from  the  wall. 

(2)  A  wall  between  4  and  5  ft.  can  be  used  as  It  stands,  subject 
to  the  same  modifications  as  In  the  preceding  case.    (Fig.  2.) 

(3)  Between  5  and  6  ft.  a  wall  can  be  notched.  The  tops  of 
the  notches  may  be  filled  with  sand-bags,  sods,  etc.      (Fig.  3.) 

(4)  Should  the  wall  be  higher  than  6  ft.,  a  platform  or  staging 
must  be  raised  Inside  to  enable  the  men  to  fire  over  the  wall  or 
through  the  notches,  or  else  the  wall  must  be  loop-holed. 

163. — ^Loop-Holing.  Loop-holes  for  fire  should  not  be  closer 
than  2  ft.  6  in.;  ordinarily  they  should  be  3  ft.  To  find  the  height, 
Tiold  fhe  riffe  in  flie  fiosHion  intended  to  he  used. 

164.— To  make  a  loop-hole  In  a  wall  (Fig.  4),  14  In.  or  less  In 
thickness,  begin  on  the  inside,  to  prevent  the  splay  being  toward 


Defense  of  Localities.  89 

the  outside,  by  detaching  a  stretcher:  the  adjacent  header  on  the 
outside  can  then  be  knocked  out  and  the  loop-hole  roughly  shaped. 
Outside  dimensions,  4  in.  wide  by  3  in.  high.  Interior  dimensions 
will  depend  on  the  nature  of  the  ground  over  which  fire  is  to  be 
delivered.  For  horizontal  fire  increase  the  breadth,  for  elevated 
or  depressed  fire  increase  the  height. 

In  walls  of  ordinary  thickness,  a  loop-hole  can  be  made  in 
about  15  minutes,  a  notch  in  about  5  minutes. 

165.— For  a  thick  wall  (Fig.  4),  the  small  part  should  be  at  the 
center,  the  loop-hole  splayed  to  the  front  and  rear,  for  it  will  do 
this  anyway.  The  side  toward  the  enemy  may  be  stepped,  in 
order  that  bullets  striking  it  may  flatten.  Loop-holes  of  observa- 
tion should  splay  towards  the  outside. 

All  loop-holes,  when  not  in  use,  should  be  blinded. 

166.— The  height  or  position  of  the  loop-hole  is  influenced  as 
follows:— 

(1)  1  ft.  above  the  ground.  Men  lying  down  in  a  shallow  exca- 
vation. Earth  heaped  up  to  18  in.  in  rear  prevents  the  enemy 
from  using  the  loop-holes  should  he  close  on  the  wall.  The  loop- 
holes are  a  diflScult  mark  for  the  enemy  and  sentries  at  night  can 
watch  the  sky  line.  Cannot  be  used  where  ground  in  front  is 
broken. 

(2)  Loop-holes  2  ft.  3  in.  Sitting.  Position  easy,  but  must  have 
a  deep  ditch  in  front. 

(3)  Loop-holes  3  ft.  Kneeling.  Position  strained  and  must 
have  a  deep  ditch  in  front. 

(4)  Loop-holes  4  ft.  4  in.  Standing.  Good  command,  but  easier 
mark  for  enemy:  ditch  necessary,  but  not  so  deep  as  In  cases  2 
or  3. 

(5)  Loop-holes  6  ft.  or  more.  Men  standing  on  banquette.  Best 
position  for  view  or  fire;  no  ditch  in  front;  banquette  strengthens 
wall,  but  takes  longer  to  prepare  wall  in  this  manner;  more  sus- 
ceptible to  artillery  fire. 

167.— In  order  to  allow  a  double  tier  of  fire,  walls  should  be  at 
least  9  ft.  high.    (Figs.  5  and  6.) 

168.— Fences.  Fences  should  be  removed  or  left  standing 
according  to  their  position  or  direction.  Wire  fence  forms  a  good 
obstacle;  a  rail  or  plank  fence  forms  a  screen  and  may  be  banked 


PLATE  25. 


Figure  1, 


Fig^ure  2 


y^ 


Fioure  3 


Figure  6 


}  ^Figure  7- 


Figure  9. 


Figure  10. 


Defense  of  Localities.  91 

witli  earth  to  give  cover.  If  fence  is  of  stone  it  may  be  treated  as 
explained  for  walls. 

169.— Hedges.  Almost  the  same  principles  as  explained  for 
walls  apply  to  hedges.  A  hedge  primarily  acts  as  a  screen,  but  to 
resist  projectiles  must  be  banked  up  with  earth. 

Hedges  possess  the  following  advantages:  (1)  With  little  labor 
afford  good  cover.  (2)  Serve  as  a  screen  and  also  as  a  revetment. 
(3)  Act  as  an  obstacle  to  the  enemy. 

To  derive  these  advantages  hedges  can  be  treated  as  follows:— 

(1)  A  hedge  with  a  ditch  on  the  defenders'  side.  Can  be  used 
as  it  stands,  the  ditch  being  converted  into  a  trench,  widened  and 
improved  if  necessary.    (Fig.  7.) 

(2)  A  hedge  with  a  ditch  on  the  enemy's  side.  Deepen  the 
ditch  if  necessary,  and  throw  the  earth  to  the  defenders'  side  to 
give  cover.  If  this  is  not  possible,  scatter  the  earth  and  dig  a 
trench  in  rear.    (Figs.  8  and  9.) 

(3)  A  hedge  with  ditches  on  both  sides.  Deepen  the  ditch  on 
the  enemy's  side,  using  the  earth  to  obtain  cover.  Trench  on  de- 
fenders' side  may  be  deepened.    (Fig.  9.) 

(4)  Hedge  on  sloping  ground.  Gain  cover  by  a  small  trench  in 
rear;  scarp  away  the  ground  in  front,  forming  a  glacis.    (Fig.  10.) 

(5)  High  and  strong  hedges.  When  time  is  available,  may  be 
treated  as  in  Fig.  11.  This  is  advantageous  where  additional  com- 
mand is  required. 

(6)  A  sunken  road  with  hedges  on  both  sides.  Dig  a  shelter 
trench  In  rear  of  the  hedge  on  defenders'  side  and  utilize  the  earth 
to  form  a  breastwork.  Cut  down  the  hedge  .on  the  enemy's  side, 
entangling  it  to  form  an  obstacle. 

(7)  Hedge  without  ditches.  Excavate  a  shelter  trench  on  de- 
fenders' side  and  bank  up  the  earth  against  the  hedge  as  a  breast- 
work. 

Weak  places  in  hedges  should  be  closed  up  with  boughs,  stakes, 
wire,  etc.,  as  a  strong  hedge,  in  addition  to  being  a  screen,  forms  a 
very  efficient  obstacle. 

170.— Embankments  may  be  defended:— 

(1)  Narrow  Embankments.  By  occupying  the  inner  edge  bet- 
ter cover  is  obtained,  but,  unless  the  bank  is  both  low  and  narrow, 
there  is  a  dead  space  in  front  at  the  foot  of  the  outer  slope.  (PI. 
25,  Fig.  1.) 


92  Defense  of  Localities. 

(2)  Broad  Embankments.  By  occupying  the  front  edge,  a  bet- 
ter field  of  fire  is  obtained,  but  less  cover  can  be  provided  for 
the  firing  line,  and  the  supports  are  exposed  when  coming  into 
action.    (Fig.  2.) 

171.— Cuttings  are  usually  defended  on  the  defenders'  side, 
since  in  this  case  retreat  is  easy  and  the  cutting  itself  forms  an 
obstacle  to  the  enemy's  advance.  But  for  active  defense  the  front 
edge  may  be  held,  and  then  a  forward  movement  is  possible.  In 
this  case  a  means  of  retreat  must  be  provided. 

172.— Fig.  3  shows  a  case  where  the  fall  of  the  ground  admits 
of  both  sides  of  the  cutting  being  occupied,  giving  a  double  tier  of 
fire.  The  command  of  the  higher  edge  over  the  lower  should  be 
about  6  ft. 

173.— In  case  of  a  road  cut,  as  in  Fig.  4,  the  upper  fence  may 
be  used  to  sustain  a  breastwork,  while  the  hedge  below  may  be 
converted  into  an  obstacle. 

174.— Woods.— (PL  26,  Fig.  6.)  Preparation  of  edge  of  wood 
occupied.  The  edge  of  a  wood  should  be  put  in  a  state  of  de- 
fense and  an  abatis  is  the  readiest  means  of  doing  it.  The  sali- 
ents should  first  be  prepared,  the  reentrants  next,  and  then  roads 
entering  the  wood  from  the  enemy's  side.  Instead  of  an  abatis, 
the  outer  trees  may  be  left  standing  and  an  entanglement  made 
by  packing  in  among  them  smaller  trees  cut  about  10  to  20  paces 
to  the  rear.  This  clearing  will  serve  as  a  communication  all  round 
the  edge  of  the  wood. 

If  a  reentrant  bend  is  deep  the  abatis  or  entanglement  may  be 
carried  straight  across  it  and  flanked  from  the  adjacent  salients. 
In  case  of  a  road,  a  lunette  may  be  used  instead  of  the  abatis  or 
entanglement.  In  case  there  is  not  time  to  prepare  the  entire 
edge  of  the  wood,  the  salients  may  alone  be  prepared,  the  flanks 
of  the  defense  being  turned  back  for  a  short  distance  into  the 
wood. 

175.— Preparation  of  woods  lying  beyond.  Woods  beyond, 
within  rifle  range  of  the  line  of  defense,  but  too  far  to  the  front  to 
be  occupied,  and  too  extended  to  be  felled,  should  have  an  abatis 
or  entanglement  on  the  rear  side  to  act  as  an  obstacle. 

176.— Cover.  Trench  digging  is  difficult  on  account  of  the 
roots,  but  when  possible  it  should  be  done.  Cover  is  generally 
obtained  from  the  natural  features.    Trees,  unless  very  large  and 


PLATE  26. 


Fig.  6. 


94  Defense  of  Localities, 

standiug  thickly,  do  uot  give  complete  protection  against  artillery 
lire.  Troops  as  supports  and  reserves,  if  not  so  far  to  the  rear  as 
to  preclude  their  seeing  through  the  wood  to  the  front,  may  be 
covered  by  log  walls  and  trenches. 

177. — communications,  (a)  There  must  be  good  radial  com- 
munication as  well  as  free  movement  along  the  boundary  in  rear 
of  the  firing  line. 

(h)  Roads  and  paths  for  bringing  up  the  supports  must  be  clear- 
ly marked  by  blazing  as  well  as  by  posting  sentries  at  all  cross 
roads. 

(c)  In  dense  woods,  preparations  should  be  made  for  blocking 
up  roads  by  cutting  trees  on  either  side  of  them  nearly  through, 
to  be  pulled  down  across  them  in  case  of  retreat. 

178.— Second  and  third  lines  may  be  placed  along  any  open 
space,  brook,  or  broad  road,  parallel  to  the  front.  In  case  of  brook, 
the  brook  should  be  in  front  of  defenders*  position. 

179.— Artillery  should  generally  be  placed  outside  of  the 
wood  on  the  flanks.  If  placed  in  the  wood,  batteries  should  be 
placed  far  apart,  near  good  roads,  masked  as  much  as  possible, 
and  each  gun  having  more  than  one  position.  Reentrants  are 
desirable. 

The  number  of  defenders  is  estimated  at  2  to  3  men  per  yard  of 
front. 

180.— Stockades.  Stockades  are  timber  defenses,  made  by 
placing  one  or  more  rows  of  timbers  or  rails  upright  or  horizon- 
tally, and  so  close  to  one  another  as  to  keep  out  rifle  bullets,  loop- 
holes being  made,  through  which  flre  is  delivered.  They  have  the 
advantages  of  combining  a  parapet  and  an  obstacle  in  one,  giving 
good  cover  and  ample  interior  space,  and  of  being  easily  guarded 
against  surprise.  On  the  other  hand,  they  require  considerable 
time  for  construction,  a  certain  amount  of  skilled  labor,  and  are 
easily  destroyed  by  artillery  fire. 

181.— Stockades  would  be  employed:— 

(1)  Where  timber  is  plentiful. 

(2)  When  artillery  fire  is  not  to  be  resisted. 

(3)  When  acting  purely  on  the  defensive.  They  are  useful  for 
the  rear  faces  or  gorges  of  half-closed  works,  and  may  be  a  good 
deal  used  in  the  defense  of  houses,  streets,  villages,  and  even  woods. 


Defense  of  Localities.  95 

182.— stockades  of  vertical  timbers.  Vertical  timbers  should 
be  close  together,  planted  iu  the  ground  to  a  depth  of  3  or  4  ft, 
according  to  their  size  and  weight,  pointed  or  spiked  at  the  top, 
and  loop-holed  at  intervals.  A  ribband  must  be  spilled  along  the 
inside,  near  the  top,  to  keep  the  timbers  close  together. 

183.— PI.  25,  Figs.  5,  G,  and  7,  show  stockades  with  squared  tim- 
bers; Fig.  8  with  round  timbers  squared  where  they  touch  and  the 
joint  between  every  two  trees  made  good  on  the  inside  by  a 
smaller  tree. 

184.— The  loop-holes  should  be  made  in  the  crack  between  the 
timbers,  in  order  to  avoid  weakening  them,  half  being  cut  out  of 
each.  (Fig.  9.)  In  round  timber,  two  saw  cuts  will  make  a  loop- 
hole.   (JFig.  10.) 

185.— The  loop-holes  should  be  cut  before  the  timbers  are  placed 
in  position  and  the  same  precautions  in  regard  to  them  as  given 
in  walls  should  be  observed.  A  loop-hole  can  be  cut  in  from  10  to 
15  minutes. 

186.— In  the  foregoing  cases,  where  the  stockade  is  built  of  tim- 
bers placed  vertically,  squared  timbers  are  preferred,  as  they  are 
more  easily  fastened  together  and  the  joints  made  bullet-proof. 
In  round  timbers  the  logs  should  be  as  straight  as  possible.  If 
very  crooked,  two  complete  rows  will  be  required. 

One  N.  C.  O.  and  10  men  will  erect  15  running  feet  of  stockade 
of  squared  timber,  with  one  tier  of  loop-holes,  in  8  hours. 

187.— Stockades  of  horizontal  timbers,  iron  rails,  fascines,  or 
logs.    (PL  26.) 

Fig.  1  shows  stockade  of  rails  and  ties.  Can  only  be  used  for  a 
very  short  distance,  as  it  will  involve  an  immense  amount  of  plant. 
Can  be  used  to  cover  guns,  close  a  road,  and  is  more  properly  a 
barricade. 

Fig.  2  shows  a  stockade  or  log  breastwork,  banked  in  rear  with 
earth  held  in  place  by  planks  or  hurdles  and  stakes. 

Fig.  3  shows  a  stockade  or  breastwork  of  logs  and  fascines. 

188.— Stockade  work,  both  vertical  and  horizontal,  can  be  used 
for  the  construction  of  tambours  (Figs.  4  and  5)  and  caponiers  for 
flanking  walls  or  stockades  and  covering  entrances.  Tambours 
may  be  triangular  or  rectangular  in  shape,  arranged  for  one  or  two 
tiers  of  fire,  and  covered  with  a  splinter-proof  roof. 
-7- 


96  Defense  of  Localities. 

189.— Buildings.  Buildings  may  be  used  for  defense,  either 
singly  or  in  combination;-- 

(aj  As  tactical  points  in  the  battle-field,  held  either  as  advanced 
posts,  or  as  supporting  points  in  the  line  or  on  the  flanks,  or  as 
rallying  points  to  cover  retreat. 

(bj  As  keeps  to  a  more  extensive  position,  such  as  a  wood,  vil- 
lage, etc. 

(cj  As  an  isolated  post  on  the  lines  of  communication. 

190.— In  order  to  admit  of  use  as  a  defensible  post,  a  building 
should  possess  the  following  requisites:— 

(1)  Solidly  built  of  soft  stone,  brick,  or  adobe. 

(2)  Large  enough  to  hold  at  least  half  a  company. 

(3)  Sheltered  from  distant  artillery  fire;  otherwise  the  building 
cannot  be  held  against  infantry  or  cavalry. 

(4)  Well  selected  for  the  object  in  view. 

(5)  Low,  flat  roof. 

(6)  Clear  field  of  fire  obtainable. 

(7)  Shape  in  plan  affording  flank  defense. 

191.— The  building  should  be  looked  upon  as  a  keep,  or  second 
line  of  defense,  a  first  line  being  prepared  at  a  minimum  distance 
of  40  yds.  to  the  front,  this  distance  being  the  least  that  will 
give  the  defenders  immunity  from  splinters  caused  by  shells  strik- 
ing the  building. 

192.— In  falling  back,  the  first  line  should  retreat  pasty  not 
into  the  house,  which  should  by  this  time  be  occupied  by  the  sup- 
ports. The  garrison  of  the  house  may  be  estimated  at  two  men  to 
each  door,  window",  or  loop-hole,  with  a  reserve  of  one-fourth,  tac- 
tical unity  being  in  this,  as  in  all  similar  cases,  adhered  to  as  much 
as  possible. 

193.— The  following  are  the  steps  which  must  be  taken  in  has- 
tily preparing  a  house  for  defense:— 

(aJ  Remove  the  inhabitants,  also  all  easily  combustible  mate- 
rial, and  provide  water  and  heaps  of  earth  in  each  room. 

(b)  Barricade  doors  and  ground-floor  Tvindows  (bullet-proof  if 
possible),  also  mask  inaccessible  window^s,  and  remove  all  glass. 

(c)  Make  loop-holes  in  doors,  shutters  and  walls,  and,  in  the 
case  of  a  sloping  roof,  remove  tiles  or  slates. 


Defense  of  Localities.  97 

(dj  Clear  away  cover  in  the  viciuity  as  far  as  time  and  means 
will  allow. 

(ej  Open  up  communication  throughout  and  prepare  a  means  of 
retreat. 

194.— The  same  precautions  as  to  loop-holing  walls  apply  in  case 
of  buildings.  On  the  ground  lioor  the  horizontal  dimensions  of  a 
loop-hole  should  be  greatest;  on  upper  floors,  the  vertical  dimen- 
sion. If  an  artillery  attack  is  feared,  shelter  trenches  should  be 
provided  outside  the  building  on  the  flanks. 

195. — Barricades  for  Doors  may  be  made  in  the  following 
ways:— 

(a)  Fill  boxes,  barrels,  cupboards,  etc.,  with  earth  and  place 
them  against  the  door  inside. 

(h)  Build  a  wall  of  brick,  stone,  flag-stones,  or  hearth-stones, 
against  the  door  inside,  and  support  by  a  shutter  or  another  door. 

(c)  If  railway  plant  is  available,  pile  ties  horizontally  on  one 
another  and  secure  with  telegraph  wire. 

(d)  Pile  lumber  inside  the  door  and  fix  with  blocks  nailed  to 
the  floor. 

(e)  Other  methods  may  be  employed  in  accordance  with  mate- 
rial available. 

196.— Should  a  door  be  reserved  for  use,  it  should  be  in  a  re- 
entering angle  of  the  building,  if  possible,  and  protected  from  fire. 
A  couple  of  chests  filled  with  earth  and  placed  on  rollers  may  be 
used  to  secure  the  door.  Similarly  it  may  be  possible  to  place  iron 
or  wood  on  the  door,  thus  rendering  it  bullet-proof. 

197.— Windows.  Windows  must  be  barricaded  as  explained 
for  doors.  If  provided  with  shutters,  these  should  be  utilized. 
Upper  windows  require  to  be  bullet-proof  only  high  enough  to 
cover  the  defenders.  Bedding  is  no  protection  against  modern 
rifles,  but  may  be  used  to  mask  windows  of  upper  floors.  If  tim- 
ber is  used  it  should  be  placed  vertically  and  nailed  to  horizontal 
ribbands  strutted  back  to  the  floor. 

198.— If  the  house  is  large  and  strong  and  is  to  be  held  to  the 
last,  in  addition  to  the  foregoing  the  following  preparations  should 
be  made:— 

(1)  Arrange  for  storage  of  provisions  and  ammunition. 

(2)  Set  apart  a  place  for  a  hospital. 


PLATE  27 


Pig.l 


Pig  2 


Kff.e, 


Defense  of  Localities.  91i 

(3)  Prepare  latrines. 

(4)  Loop-hole  partition  walls  and  upper  floors. 

(5)  Make  ready  barricades  to  cover  retreat  from  one  part  of  the 
building  to  another. 

(6)  If  artillery  is  feared,  shore  up  the  floors  and  cover  them 
with  about  3  in.  of  earth. 

199.— Should  the  construction  of  the  house  not  afford  suffi- 
cient flank  defense,  it  can  be  improvised  in  the  shape  of  tambours 
or  caponiers,  but  the  labor  involved  in  their  construction  is  consid- 
erable and  they  would  only  be  undertaken  for  the  defense  of  a 
very  long  wall  or  to  cover  an  important  entrance  or  communi- 
cation. 

For  the  latter  purpose  a  machicouUs  gallery  is  sometimes  em- 
ployed. (PI.  27,  Fig.  3.)  This  is  made  by  removing  the  wall  of 
the  upper  story  where  a  window  occurs  down  to  the  level  of  the 
floor,  running  out  two  or  three  long  balks  so  as  to  project  a  few 
feet  beyond  the  wall,  the  other  ends  being  secured  down  to  the 
floor.  On  these  planks  are  nailed,  with  holes  cut  through  to  act 
as  loop-holes,  and  a  musket-proof  parapet  of  planking,  sand-bags, 
etc.,  is  built  all  around.  A  projecting  veranda  offers  a  favorable 
position  for  this  arrangement. 

Second  method:  If  a  regular  gallery  can  not  be  made,  holes 
may  be  cut  in  the  wall  at  a  convenient  height  for  a  man  to  fire 
downwards  when  leaning  over,  and  a  screen  of  wood  or  other 
material  may  be  secured  outside  for  protection.    (Fig.  4.) 

If  neither  of  the  foregoing  methods  be  possible,  holes  may  be 
made  in  the  roof,  through  which  grenades  may  be  thrown  on  the 
enemy. 

200.— The  materials  most  likely  to  be  useful  in  preparing  a 
house  for  defense  are  sand-bags,  stout  timbers,  such  as  railway 
ties,  large  boxes,  chests,  barrels,  coal-boxes,  furniture  and  bed- 
ding. 

201.— PI.  27,  Figs.  1,  2,  and  5,  illustrate  the  more  important 
points  in  the  defense  of  a  house. 

202.— Farms.  Farms  should  be  defended  according  to  the 
nature  of  the  surface  covering,  the  ground  and  the  improvements, 
and  may  involve  the  preparation  for  defense  of  walls,  hedges,  cut- 
tings, embankments,  buildings,  woods,  etc.  Owing  to  their  posi- 
tions, farms  may  become  very  important  and  a  great  amount  of 


100  Defense  of  Localities. 

fighting  take  place  for  their  possession.  They  may  occur  either 
in  the  main  line  of  a  position,  as  an  advanced  post  in  front,  or  as  a 
reserve  station  or  rallying  point  in  rear. 

203.— Fig.  6  shows  the  principles  of  defense  applied  to  a  farm 
lying  in  advance  of  a  stream,  which  is  a  point  that  requires  to  be 
strongly  held.  From  the  position  of  the  farm  it  must  be  held  Jife 
an  advanced  post. 

The  firing  line  is  established  along  the  fences  bounding  the 
fields  and  orchard.  The  farm  buildings  are  loop-holed  and  can 
be  held  should  the  firing  line  be  forced,  while  the  fire  from  the 
house  would  render  occupation  of  the  farmyard  by  the  enemy 
difiicult.  Further  to  the  rear,  the  wood  is  strongly  prepared  for  a 
final  position,  as  shown  in  the  figure. 

204.— The  rear  of  an  advanced  post  should  be  left  weak  and 
open  to  facilitate  recapture. 

205.— Villages.  Villages  can  be  rapidly  prepared  for  defense 
and,  under  favorable  circumstances,  obstinately  defended;  conse- 
quently they  are  valuable  supporting  points  in  a  defensive  line. 
Owing  to  the  effect  of  modern  artillery  and  the  liability  of  burst- 
ing shells  to  set  villages  on  fire,  great  precautions  have  to  be  taken 
in  the  preparation  for  defense. 

206.— A  village,  when  properly  prepared  and  defended,  may 
have  the  following  advantages:— 

(a)  Can  be  rapidly  placed  in  condition  for  defense. 

(h)  Defense  may  be  obstinate — thus  giving  time. 

(c)  Conceals  the  strength  of  the  defenders. 

(d)  Provides  a  certain  amount  of  cover  rfrom  fire. 
(ej  Shelter  from  the  elements. 

On  the  other  hand:— 

(a)  The  garrison  is  scattered,  and  hence  the  difllculty  of 
supervision. 

(b)  When  under  artillery  fire,  splinters  may  cause  many 
casualties. 

fc)  Liability  to  be  set  on  fire  by  shells. 

207.— A  village  may  be  held  with  the  following  objects  In 
view:— 

fa)  As  a  supporting  point  in  the  main  line  of  defense. 
(h)  As  an  advanced  post  in  front  of  the  main  line. 


PLATE  2&,  ,  .'. 


102)  D^pyfenee  of  Localities.  "^ 

(0)  As  an  independent  post. 

(d)  As  a  reserve  station  or  rallying  point  in  rear. 

In  the  first  case,  strengthen  the  front  and  flanks.  The  rear 
should  be  prepared  to  resist  infantry.  In  the  second  case,  the 
distance  from  the  main  line  will  govern  the  amount  of  prepara- 
tion. If  very  distant,  should  be  prepared  for  all-round  defense. 
If  within  rifle  range,  the  rear  should  be  left  open,  so  that  in  case 
the  village  is  taken,  recapture  will  be  facilitated.  In  the  third 
case,  if  an  independent  post,  must  be  prepared  for  an  all-round 
defense.  In  the  fourth  case,  if  in  the  rear  of  the  main  line,  must  be 
prepared  for  a  protracted,  all-round  defense. 

208.— -Whether  or  not  a  village  is  to  be  held  will  depend  on:— 

(1)  Its  tactical  value  as  compared  with  the  number  of  men  re- 
quired to  defend  it. 

(2)  Whether  it  is  practicable  to  provide  a  suflScient  garrison  for 
its  defense. 

(3)  Whether  It  will  be  possible  to  demolish  the  village  entirely, 
in  order  to  deprive  the  enemy  of  the  cover  It  provides. 

(4)  On  the  form  and  nature  of  the  surrounding  country— i.  6., 
no  commanding  ground  within  artillery  range,  foreground  easily 
prepared  and  the  unimpeded  advance  of  the  defenders'  troops  In 
the  required  direction  easily  arranged. 

(5)  On  the  shape  of  the  village— whether  broadside,  salient,  or 
circular. 

(6)  Nature  and  materials  of  the  houses. 

209.— The  first  points  to  determine  in  preparing  a  village  for 
defense  are  how  much  of  it  will  be  defended,  whether  there  are 
buildings  suitable  for  a  keep  or  citadel,  and  whether  or  not  these 
are  properly  located. 

210.— The  arrangements  for  defense  would  be  made  in  the  fol- 
lowing order:— 

(1)  Clear  the  ground  toward  the  enemy.    (See  Chap.  V.) 

(2)  Cover  for  the  firing  line,  supports,  and  reserves.  (See 
Chap.  IV.) 

(3)  Creating  obstacles.    (See  Chap.  VI.) 

(4)  Preparing  communications.    (See  Chap.  XVII.) 

(5)  Constructing  retrenchments,  citadels,  or  keeps.  (See  "Build- 
ings.") 


Defense  of  Localities.  103 

211.— The  garrison  of  a  village  may  be  estimated  at  two  men 
to  the  yard  of  perimeter  to  be  defended. 

212.— Salient  Village.  (PL  28,  Fig.  2.)  The  successive  lines 
of  defense  must  be  carried  well  out  to  both  sides  and  the  flanks 
well  protected;  otherwise  the  enemy  may  turn  them  and  avoid 
fighting  in  the  streets. 

213.— Broadside  Village.  (Fig.  1.)  Here  the  outside  fences 
must  be  more  utilized  than  the  actual  buildings,  as  the  latter  are 
open  to  fire  from  artillery. 

214.— Circular  Village.  (PI.  29.)  Great  attention  must  be  paid 
to  the  proper  division  of  the  village  into  sections  for  defense  and 
preparing  and  making  the  communications. 

215.— In  any  of  the  foregoing  cases,  if  cover  does  not  exist  foi 
supports  and  reserves,  it  must  be  provided,  as  the  village  will  prob- 
ably be  shelled  before  being  assaulted. 

If  artillery  is  to  be  used  it  should  be  placed  on  commanding 
ground,  inaccessible,  if  possible,  to  the  enemey,  and  so  that  its 
fire  will  sweep  those  parts  most  favorable  to  the  enemy's  advance. 


PLATE  29. 


CHAPTER  XIV.— Use  of  Cordage  and  Spars. 


216.— A  rope  is  composed  of  three  or  more  strands  of  fibrous 
material,  iron  or  steel,  twisted  together.  The  strands  of  fibrous 
ropes  are  formed  of  threads;  of  iron  and  steel  ropes,  of  wires.  The 
size  of  rope  is  denoted  by  its  diameter  in  inches,*  and  rope  is  gen- 
erally sold  by  the  pound.  Fibrous  ropes  when  new  and  dry  stretch 
considerably,  when  wet  they  contract;  advantage  is  often  taken  of 
the  latter  fact  to  tighten  temporary  lashings.  Manila  rope  is  only 
about  %  as  strong  as  hemp  rope;  tarred  ropes  only  about  %  as 
strong  as  untarred. 

217,— A  rule  approximating  to  the  breaking  weight  of  a  new  rope, 
in  tons  of  2,000  lbs.,  is  to  take  one-fourth  the  square  of  the  circum- 
ference in  inched.  The  strength  of  pieces  from  the  same  coil  may 
vary  25  per  cent. 

Ropes  in  daily  use  should  not  be  worked  up  to  greater  than  1-5 
their  breaking  loads,  to  meet  the  reduction  in  strength  by  wear 
and  exposure. 

218.— The  following  table  gives  the  approximate  breaking 
loads  and  weights  of  new  Manila  ropes,  Swede's  hemp  center 
Iron  pliable  ropes  of  6  strands  of  19  wires  each,  and  hemp  center 
Steel  pliable  ropes  of  6  strands  of  19  wires  each,  Manufacturers' 
Tests: 


Diam.  ii 
inches 


Breaking  loads  in  lbs. 


1-4 

3-8 

7-16 

1-2 

5-8 

3-4 

7-8 

1 

IV4 

m 
1% 
2 


Manila 

^780" 

1,280 

1,562 

2,250 

4,000 

5,000 

7,500 

9,000 

14,000 

20,250 

30,250 

36,000 


Iron 


Steel 


Weig-ht  per  100 
ft.  in  lbs. 

Manila  |I™",t 


Minimum  Size  of 

Sheaves  in  feet 
for  Iron  and  Steel 


5,000 

6,200 

7,600 

11,000 

17,500 

23,000 

32,000 

54,000 

78,000 

108,000 

130,000 


12,000 

15,000 

24,000 

36,000 

50,000 

66,000 

104,000 

154,000 

212,000 

250,000 


^   1 

...   1 

5  1 

26 

1 

61-81 

29 

iy2 

8    ' 

35 

2 

13.5 

70 

2% 

16.5 

88 

3V4 

24 

120 

3% 

30 

158 

4 

45 

250 

5 

66 

365 

evz 

97 

525 

7% 

15     1 

630 

9 

*In  the  Navy  the  size  of  rope  is  denoted  by  its  circumference  in  inches, 
method  used  should  be  distinctly  stated. 


The 


106  Use  of  Cordage  and  ^pars. 

219.— Knots,  Hitches,  etc.  The  standing  part  of  a  rope  is  any 
part  not  an  end. 

A  bight  is  a  loop  formed  in  a  rope.    (PI.  30,  Fig.  1.) 

Whipping  is  securing  the  end  of  a  rope  with  twine  to  prevent 
it  from  fraying  out.    (Fig.  1.) 

Parceling  is  wrapping  a  rope  to  prevent  chafing  or  cutting 
against  a  rough  surface  or  sharp  edge.    (Fig.  1.) 

Stopping  is  fastening  two  parts  of  a  rope  together  without  a 
crossing  or  riding.     (Fig.  1.) 

I^eizi'ng  is  fastening  two  parts  of  a  rope  together  with  or  with- 
out riding  and  finishing  with  crossings  or  f rapping  turns.  (Figs. 
5  and  17,  f rapping  turns  not  shown.) 

Nippering  is  taking  turns  crosswise  between  the  parts  to  jam 
them,  finishing  with  crossings  or  frapping  turns,  latter  not  shown 
in  figure.    (Fig.  1.) 

Splicing  is  joining  the  ends  of  ropes  by  opening  the  strands 
and  placing  them  into  one  another  (Figs.  2  and  3),  or  by  putting 
the  strands  of  the  ends  of  a  rope  between  those  of  the  standing 
part    (Fig.  4.)    The  splice  is  about  %  weaker  than  main  rope. 

Rolli/ng  or  stopper  hitch,  for  fastening  a  rope  to  a  strap  or  tail 
block,  and  to  secure  a  fall  while  being  shifted  on  a  windlass  or 
capstan.    (Fig.  5.) 

Overhand  Icnot,  to  prevent  the  end  of  a  rope  from  fraying  out, 
from  slipping  through  a  block,  and  the  beginning  of  several  other 
knots.    (Fig.  6.) 

Figure  of  8  knot,  for  same  purpose  as  overhand  knot  and  used 
in  making  ansk  piers.     (Fig.  7.) 

Square  or  reef  knot,  for  joining  the  ends  of  two  ropes  the  same 
size.    (Fig.  8.) 

Thief  knot  (Fig.  9),  with  ends  on  opposite  sides,  and  Granny  knot 
(Fig.  10),  by  crossing  the  ends  the  wrong  way,  both  looking  like 
square  knots,  are  to  be  avoided,  as  they  will  not  hold. 

Single  how  or  slip  knot.    (Fig.  11.) 

Square  how,  which  can  be  cast  off.    (Fig.  13.) 

Marlinspike  hitch,  used  in  putting  on  lashings,  etc.    (Fig.  12.) 

Sheepshank,  used  to  shorten  a  rope  temporarily  without  cutting. 
(Fig.  14.) 

Two  half  lutches,  for  fastening  the  end  of  a  rope  around  its  own 
standing  part    (Fig.  15.) 


PLATE  30. 


» 


FIG.1. 

jjxxxnn 


IVhipping  J>*^SPV. 

IG,2. 

7 — y 


-vT'v-v^     Nipperwig 
or  Seizing  '  " 


FIG.  6. 


^""""^ Rdltng  or  i^/f/K'i  Hitch,      seizing 

^ye  Splice        Ym.  -    fIG.9.    .   FIG.  10. 


FIG.  11.,^ FIG.12. 


•FIG.8.. 


Sinole  bow  <n-skp  knot,     -n^  7l^  .^     Square  or':       Ohie/C      Granny 

FIG.  13.     __  Marli?^pvP.e  .       ^^^pjQ  ^4    ^ 


FIG.  17.  ^J^^I^^/'^^^^M^ 


Wecu/etiknot 
or  Sheet  bervd.         Bend 

FIG.22. 


Timber  hitch. 


EM_ 


PLATE  51. 


FIG.  I 


FIG,  2 


FIG  3^       FIG.4.^     FIG.5. 


on  a  bi^t 

rIG6. 


XiOrkis  he(td 

^FIQIO. 


FIG.13. 


'  Jtack  lashing^ 

nG.i5. 


licick  /askirtg- 

FIG.14. 


Square  ZMshzng- 

FIG.16. 


\ear  Lushing 


Gin   iashin^  EAJf. 


Vse  of  Cordage  and  Spars.  109 

Round  tturn  and  two  Juiif  hitches,  to  secure  guys  to  stakes,  etc. 
(Fig.  16.) 

Fisherman's  bend  or  Anchor  knot,  for  fastening  a  rope  to  an 
anctior  or  ring.    (Fig.  17.) 

Weaver's  knot  or  sheet  bend,  for  joining  ropes  of  different  sizes 
without  jamming.    (Fig.  18.) 

Double  sheet  bend,  more  secure  tlian  the  single  bend.    (Fig.  19.) 
Glove  hitch,  for  fastening  a  rope  to  a  spar;  the  end  may  after- 
wards be  stoppered  to  its  own  part.    The  clove  hitch  differs  from 
two  half  hitches  only  in  being  made  around  a  spar  cr  other  rope 
instead  of  around  its  own  standing  part.    (Fig.  20.) 

Timber  hitch  jams  when  made  round  a  timber.    (Fig.  21.) 
Bowline,  to  form  a  temporary  loop  at  the  end  of  a  rope.    (Fig. 
22.) 

Bowline  on  a  bight,  to  mal^e  a  loop  on  a  bight.    (PT.  31,  Fig  1.) 
Cafs  paw,  for  applying  a  purchase  or  tackle  to  the  fall  of  an- 
other.   (Fig.  2,  the  beginning;  Fig.  3,  how  applied.) 

Blackwall  hitch,  for  fastening  the  end  of  a  rope  on  a  block  in  the 
simplest  manner,  or  fastening  a  rope  in  a  hook.    (Fig.  4.) 

Mousing  is  a  seizing  placed  around  a  hook  to  prevent  it  from 
spreading  or  unhooking.    (Fig.  4.) 

Carrick  bend,  to  fasten  guys  to  a  derrick.     (Fig.  5.) 
Lark's  head,  for  fastening  a  bight  to  a  ring.    (Fig.  6.) 
Capstan  or  Prolonge,  making  fast  a  spar.    (Fig.  7.) 
Wall  knot,  for  finishing  off  the  end  of  a  rope  to  keep  from  un- 
stranding  (Fig.  8),  by  passing  the  strands,  as  shown,  then  drawing 
them  down  into  a  knot. 

Frapping  is  passing  a  rope  around  a  lashing  to  keep  the  turns 
together.    (Figs.  14,  15  and  16.) 

Straps  are  rings  used  for  attaching  tackles  to  spars  or  ropes. 
(PI.  33,  Figs.  1,  2  and  6.) 

220.— To  make  a  short  splice.  (PL  30,  Fig.  2.)  Unlay  strands 
of  each  end  for  a  convenient  length;  take  an  end  in  each  hand, 
place  end  to  end,  strands  sandwiching,  and  grasp  the  three  strands 
from  opposite  rope  in  left  hand.  Take  a  free  strand,  pass  it  over 
the  first  strand  next  to  it,  then  through  under  the  second  and  out 
between  the  second  and  third  from  it,  then  haul  taut.  Pass 
each  of  the  remaining  six  strands  in  same  manner,  first  those  of 


110  Use  of  Cordage  and  Spars. 

oue  end  and  then  tliojse  ot  the  other,  and  bo  continue  as  far  as 
desired. 

221.— To  make  a  long  splice.  (1^  ig.  3.)  Unlay  strands  of  each 
end,  three  or  four  times  longer  than  for  short  splice,  and  place  end 
to  end  as  described.  Unlay  one  strand  a  considerable  distance  and 
fill  up  its  space  with  opposite  strand  from  other  rope,  and  twis» 
them  together.  Do  the  same  with  two  strands  on  other  rope. 
Open  remaining  strands,  divide  in  two,  make  overhand  knot  with 
opposite  halves,  and  lead  ends  as  in  short  splice.  Cut  off  the  other 
two  halves.  Do  the  same  with  the  other  pairs  of  strands 
where  twisted  together.  Before  cutting  off  any  of  the  half  strands, 
first  stretch,  roll  under  the  feet,  and  pound  the  rope  well.  This 
splicing  does  not  increase  the  size  of  the  rope  and  is  used  where 
the  splice  is  to  run  through  blocks. 

222.— To  make  an  eye  splice.  (Fig.  4.)  •  Unlay  one  end  for 
ghort  distance,  lay  strands  upon  the  standing  part  so  as  to  form 
the  desired  sized  eye.  Put  first  end  through  the  strand  next  to 
it.  Put  second  over  that  strand  and  through  second.  Put  third 
through  third  strand  on  other  side  of  rope  and  so  continue.  This 
forms  a  permanent  loop  in  end  of  rope. 

223.— To  sling  a  box  or  barrel.  Lay  a  strong  strap  under 
it,  spreading  the  parts,  and  pass  one  bight  through  the  other;  or 
make  a  long  loop  with  a  bowline  and  sling  as  shown  on  PI.  31, 
Fig.  9.  If  one  head  is  out  stand  barrel  up,  put  one  part  of  a  strap 
under  middle  of  bottom,  take  a  half  hitch  over  top  with  each  part 
just  over  bilge  hoops  and  exactly  opposite;  or  place  rope  under 
barrel,  bring  up  over  top,  make  overhand  knot,  open  it  out  and  slip 
each  half  down  over  hoops,  fasten  end  to  standing  part  with  bow- 
line.   (Fig.  10.) 

224.— Rack  lashings  (Figs.  11,  12  and  13)  are  made  with  a  1-3 
in.  rope,  18  ft.  long,  with  a  loop  at  one  end,  and  a  rack  stick  2  ft. 
long,  1%.  in.  in  diameter,  having  a  cord  4  ft.  long  through  one  end, 
by  passing  the  rope  two  or  three  times  around  the  side  rail  and 
balk,  and,  after  making  it  fast,  twisting  It  tightly  with  the  rack 
stick. 

225.— Transom  lashing.  (Fig.  14.)  The  spars  are  laid  across 
each  other  at  right  angles,  a  clove  hitch  is  made  on  one  of  the 
spars,  the  end  then  twisted  around  its  standing  part,  then  three 


2L4IE'32. 


FIG.1.  _FI&2        PIG.3.  •        FIG.4. 


FIG.  7. 


Sinole 


vket     lafiecket  \t\ 


pZ  rfr       Treble, 

rullet,         gock         block 

FIG  6. 


FIGS. 


(TtT/,  7       Hrry Block 


FIG.IO 


112  Use  of  Cordage  and  Spars. 

or  more  turns  are  taken  around  ibe  spars,  under  one  and  over  the 
other,  keeping  outside  previous  turns  on  one  spar  and  inside  on  the 
other.  Several  trapping  turns  are  then  talien  between  the 
spars  and  the  end  fastened  on  one  of  the  spars  with  a  clove 
hitch.    Used  in  lashing  transoms  to  standards  in  bridge-building. 

226.— Shear  lashing.  (Fig.  15.)  The  spars  are  laid  parallel,  a 
couple  of  inches  apart,  on  a  block,  a  clove  hitch  made  on  one  spar, 
then  five  or  six  turns  taken  ai'ound  both  spars  without  riding. 
Several  frapping  turns  are  then  taken  between  the  spars  and  the 
end  fastened  on  one  of  the  spars  with  a  clove  hitch.  This  is  used 
in  rigging  shears  for  hoisting  heavy  weights,  etc. 

227.— Gin  lashing.  (Fig.  IG.)  The  three  spars  are  laid  par- 
allel, a  couple  of  inches  apart,  the  butts  of  the  two  outside  ones 
in  one  direction,  that  of  the  middle  one  in  the  opposite  direction. 
A  clove  hitch  is  made  on  one  spar,  then  five  or  six  loose  turns 
taken,  passing  over  and  under,  without  riding.  Several  frapping 
turns  are  taken  in  each  interval  and  the  end  fastened  on  one  of 
the  spars  with  a  clove  hitch. 

228.— Blocks,  Tackles,  etc.  A  pulley  consists  of  a  wheel,  hav- 
ing a  grooved  rim  for  carrying  a  rope,  turning  in  a  frame.  (PL 
32,  Fig.  1.) 

A  block  (Figs.  2  and  3)  consists  of  one  or  more  grooved  pulleys 
or  sheaves  turning  on  an  axle,  called  a  pin,  mounted  in  a  casing 
or  shell,  which  is  furnished  with  a  hook,  eye  or  strap  on  one  end, 
by  which  the  block  may  be  attached  to  something,  and  sometimes 
with  a  becket  on  the  other  end  for  attaching  ropes,  etc.  It  is 
used  to  transmit  power,  or  change  direction  of  motion,  by  means 
of  a  rope  or  chain  passing  round  the  movable  pulleys.  Blocks  are 
single,  double,  treble  or  fourfold,  according  as  the  number  of 
sheaves  or  pulleys  is  one,  two,  three  or  four.  The  size  of  blocks 
is  expressed  by  the  length  of  the  shell  in  inches.  A  common  style 
of  Ferry  Block  is  shown  in  Fig.  5. 

A  snatch  block  (Fig.  4)  is  a  single  block  with  a  notch  cut  in  one 
cheek  so  as  to  receive  the  standing  part  of  a  fall  without  the  trou- 
ble of  reeving  and  unreeving  the  whole. 

A  running  block  is  one  attached  directly  or  indirectly  to  the  ob- 
ject to  be  raised  or  moved;  a  standing  block  is  one  fixed  to  some 
permanent  support. 


Use  of  Cordage  and  Spars,  1 1 3 

229.— A  tackle  consists  of  two  or  more  blocks  with  a  rope  rove 
ttirougii  tliem  for  use  in  lioisting. 

230.— Tlie  parts  of  all  ropes  between  the  points  of  fastening 
and  sheaves  are  called  standing  parts;  the  parts  between  the 
sheaves  are  called  running  parts;  the  part  to  which  the  power  is 
applied  is  called  the  fall. 

231.— To  overMul  a  tackle  is  to  separate  the  blocks;  to  round  in 
is  to  bring  the  blocks  closer  together. 

A  tackle  is  said  to  be  block  and  Uock  or  two  blocks  when  the  en- 
tire fall  is  hauled  through  so  the  blocks  are  in  contact. 

232.— Before  reeving  a  rope  in  a  block,  it  should  be  stretched 
out  its  full  length.  Tackle  should  not  be  allowed  to  twist;  to  pre- 
vent it,  insert  a  bar  in  the  block  or  between  the  running  parts  and 
use  it  as  a  lever  to  hold  straight.  If  allowed  to  make  one  complete 
turn  with  two  single  blocks,  the  friction  will  increase  the  resist- 
ance about  40  per  cent.  Ropes  should  not  be  too  large  for  blocks, 
the  rule  being,  ''Small  ropes  and  hig  blocks.^' 

233.— Power  of  Tackle.  Theoretically,  the  power  necessary 
to  just  balance  a  weight,  with  a  tackle  of  two  blocks,  is  equal 
to  the  weight  divided  by  the  number  of  ropes  at  the  running 
block,  including  the  standing  part  if  attached  to  it. 

234.— To  produce  motion,  however,  a  greater  power  is  required 
to  overcome  friction  and  stiffness  of  rope.  It  has  been  found  by  ex- 
periment that  to  do  this  about  10  per  cent  of  the  theoretical  power 
necessary  to  balance  must  be  added  to  itself  for  each  of  the 
sheaves  over  which  the  rope  passes,  the  blocks  being  in  good  con- 
dition and  well  oiled.  If  not  in  good  condition  and  not  well  oiled, 
the  per  cent  may  be  as  high  as  30  for  each  sheave. 

235.— The  formula  P  =  ^^^^  is  used  to  determine  the  power 
required  to  raise  a  weight  with  a  simple  tackle,  in  which  P  =  the 
power  required,  W  =  the  weight  to  be  raised,  S  =  the  number 
of  sheaves,  and  R  =  the  number  of  ropes  at  running  block,  in- 
cluding standing  part  if  attached  to  it.  If  it  is  required  to  find 
how  great  a  weight  a  certain  power  will  lift,  the  formula  is 
W  =^3^.  Power  is  gained  only  at  the  loss  of  time.  The  power 
moves  as  many  times  faster  and  farther  than  the  weight  as  the 
number  of  ropes  at  the  running  block.    No  advantage  is  gained 


PLATE  33. 


Use  of  Cordage  and  Spars.  115 

by  using,  in  one  fall,  a  greater  number  of  sheaves  than  two 
treble  blocks,  but  further  advantage  may  be  gained  by  a  combina- 
tion of  blocks  and  tackles.* 

236.— A  squad  of  men  hauling  on  a  fall  exert  a  pull  of  about 
80  lbs.  (or  half  their  weight)  each,  the  fall  being  nearly  horizontal. 

237.— A  Derrick  (Fig.  7)  usually  consists  of  a  single  spar  or 
leg,  held  up  by  four  guys,  and  having  a  tackle  lashed  to  the  top, 
used  for  hoisting  or  lowering  heavy  bodies  within  a  circle  whose 
diameter  equals  %  the  height  of  the  spar.  When  made  of  two 
legs  (Fig.  8),  they  are  mortised  into  a  cap  on  top  and  a  sill  at  the 
bottom,  only  two  guys  being  required,  a  fore  and  back,  but  three 
are  better,  one  fore  and  two  back.  The  weight  can  only  swing 
between  the  legs.  The  holdfasts  for  the  guys  should  be  at  a  dis- 
tance from  foot  of  derrick  at  least  twice  its  height.  The  foot 
should  be  secured  from  slipping  by  being  let  into  a  hole  in  the 
ground  or  otherwise. 

238.— Shears  (PI.  33,  Fig.  1)  consist  of  two  spars,  of  a  size  suita- 
ble for  the  weight  to  be  raised,  lashed  together  at  the  cross. 

A  tackle  is  fastened  at  the  lashing  by  a  strap  passed  around  it 
or  otherwise,  the  hook  moused,  and  holdfasts  are  required  as  for 
two-legged  derrick. 

Two-legged  derricks  and  shears  should  not  lean  to  exceed  1-3 
of  their  height,  and  each  leg  should  have  about  %  this  Inclination, 
or  1-6  their  height. 

239.— A  Gin  (Fig.  2)  is  a  tripod  formed  of  three  poles.  The  two 
outside  ones  are  called  legs,  the  third  one  the  pry-pole.  Gins  re- 
quire no  guys.    Weights  can  only  be  lifted  vertically. 

240.— In  using  derricks,  shears,  and  gins,  the  fall  is  generally 
led  through  a  snatch-block  lashed  on  a  leg  near  the  bottom, 
thence  to  a  crab,  windlass,  or  capstan.  Derricks  frequently 
have  fastened  on  their  legs  a  winch  for  transmitting  the  power. 
(PI.  32,  Fig.  10.) 

241.— A  "Windlass  (Fig.  12)  consists  of  a  horizontal  axis  fast- 
ened in  a  frame  and  turned  by  means  of  cranks  or  handles.  The 
rope  may  either  be  fastened  to  the  axis  or  passed  two  or  three 
times  around  it,  hauled  taut,  the  free  end  being  held,  and  taken 
in  by  men  in  the  rear. 


*The  formula    P  =  — ^^-^     is    merely   a    simplified    form    of    the    equation 
p  =  ( W  -{-  rV  W  S  )    -^  R.      (See  par.  234.) 


116  Use  of  Cordage  and  Spars, 

242.— A  Capstan  (PI.  32,  Fig.  9,  and  PI.  33,  Fig.  3)  consists  of 
an  upright  barrel,  either  smooth  or  ribbed,  arranged  about  a  spin- 
dle. Above  the  barrel  is  the  head  with  holes  to  receive  the  ends  of 
levers  or  bars  by  which  the  barrel  is  revolved.  The  rope  is  passed 
and  held  as  explained  for  a  windlass. 

243.— Holdfasts  are  stout  wooden  stakes  driven  into  the 
ground,  or  other  arrangements  used  for  securing  purposes. 

An  essential  point  to  be  considered  before  moving  or  suspend- 
ing heavy  weights  is  the  nature  and  condition  of  the  securing 
points,  together  with  the  strain  that  will  be  brought  upon  them. 
In  the  first  instance,  it  is  better  to  make  them  more  secure  than 
seems  to  be  absolutely  necessary,  as,  when  they  once  begin  to 
give  way,  it  is  difficult  to  strengthen  them.  PI.  33,  Figs.  4,  5.  6 
and  7,  show  some  of  the  various  methods  of  making  them, 
also  PI.  40a. 

243a.— An  improvised  Field  Capstan,  which  is  but  an  adapta- 
tion of  the  Spanish  windlass,  is  shown  in  cut.  One  end  of  the  rope 
is  made  fast  to  the  object  which  is  to  be  moved  and  the  other  end 
to  a  holdfast.  A  lever,  a,  is  inserted  in  a  bight  of  the  rope  and  one 
end  of  it  placed  against  an  upright  bar,  h.  The  lever  is  then  car- 
ried round  and  round  the  bar,  which  revolves  and  gradually  winds 
the  rope  upon  itself  as  it  approaches  the  holdfast.  The  bar  h  can 
be  held  upright  more  readily  if  the  lever  a  is  long  enough  for  men 
to  work  at  both  ends  of  it. 


PLATE  3^. 


M0 
*iil: 


CHAPTER  XV.— Spar  Bridges. 

244.— Military  Bridges  are  not  required  to  fulfill  all  the  condi- 
tions of  ordinary  bridges.  Tliey  are  constructed  for  special  and 
immediate  purposes,  usually  with  unskilled  labor,  and  of  such 
materials  as  can  be  procured  on  or  near  the  spot.  That  the  bridge 
built  shall  be  strong  enough  to  bear  the  heaviest  load  intended  to 
be  crossed  is  the  first  requisite;  celerity  and  simplicity  of  con- 
struction next. 

245.— PI.  34  is  an  illustration  of  what  was  done  in  building 
Military  Railroad  Bridges  under  unfavorable  circumstances  in 
time  of  war  with  troops  of  the  line,  very  few  of  whom  were 
mechanics,  many  could  not  even  handle  an  ax,  none  were  trained 
to  the  duty,  and  none  were  engineer  troops.  This  bridge  was  built 
by  General  Haupt  over  Potomac  Creek,  Va.,  during  the  Rebellion, 
and  was  80  ft.  high  and  400  ft.  long.  It  consisted  of  three  tiers 
of  trestles  on  top  of  cribs  12  ft.  high.  The  timber  used  was  chiefly 
round  sticks,  cut  in  the  woods  near  by,  and  put  together  without 
bolts,  simply  with  spikes  and  wooden  pins,  and  when  finished,  was 
crossed  by  10  to  20  heavily  loaded  trains  per  day.  This  kind  of 
work,  however,  properly  belongs  to  a  special  construction  corps, 
but  it  falls  to  the  lot  of  the  ofllcers  and  men  who  first  arrive  at  a 
stream  on  the  ordinary,  roads,  where  there  are  no  means  of  cross- 
ing, to  construct  an  improvised  bridge  with  such  tools  and  of  such 
materials  as  may  be  available. 

246.— The  plans  and  expedients  which  follow  have  been  select- 
ed with  a  view  to  their  being  types  of  bridges  that  can  be  con- 
structed by  troops  having  no  other  tools  than  axes  and  augers,  and 
such  materials  as  growing  trees  found  in  the  vicinity,  and  beams, 
boards,  ropes,  wire,  nails,  etc..  obtained  from  neighboring  houses 
and  towns.  The  purposes  for  which  the  bridge  is  to  be  used,  the 
nature  of  the  crossing,  velocity  of  stream,  and  kind  of  bottom,  will 
determine  its  strength,  kind,  size.  etc. 

247.— For  a  common  road  bridge,  the  load  is  assumed  to  be  h 
maximum  when  covererl  with  men.  estimated  at  120  lbs.  to  the 
square  foot,  Plns  the  woisrht  of  the  bridge,  usually  taken  at  about 
80  lbs.  per  lineal  foot.  For  roas^ons  which  are  evident,  the  bridge 
should  be  as  shovf  ns  possible,  with  good  approaches.  Swampy, 
high,  or  steep  banks  should  be  avoided. 

248.— Bridges  usually  take  their  names  from  some  part  of  their 


Spar  Bridges.  119 

construction,  as  Trestle,  Truss,  Pile,  Suspension,  or  Floating  Bridges. 
The  distance  between  supports  (determined  by  the  strength  of 
the  balks  to  bear  the  desired  load)  is  called  the  bay  or  spcm,  and 
the  corresponding  part  of  the  bridge  the  span.  The  superstruct- 
ure, consisting  of  the  stringers  or  balks,  the  floor,  the  side-rails 
and  the  fastenings,  is  of  the  same  nature  for  each  kind,  as  shown 
in  PI.  35,  Fig.  1.  The  ends  of  the  balks  rest  on  cross-pieces  of  the 
supports  called  transoms;  on  the  balks  (of  which  there  are  usually 
five)  are  laid  chess  or  poles,  forming  the  floor;  on  top  of  the 
floor,  over  the  outside  balks,  are  laid  side-rails  or  poles,  which 
are  securely  fastened  every  4  or  5  ft.  to  the  balks  beneath  by 
rack  lashings.  Hand-rails  (Fig.  2)  should  always  be  provided  on 
each  side  of  the  roadway.  The  usual  width  of  military  bridges  is 
9  ft.  in  the  clear,  between  side-rails;  6  ft.  will  answer  for  Infantry 
in  column  of  twos,  and  Cavalry  by  file;  2.5  ft.  for  Infantry  in 
single  file. 

249.— For  determining  the  strength  of  the  materials  to  be  used, 
all  errors  should  be  on  the  side  of  safety.  The  practical  method 
is  to  place  the  ends  of  the  timber  on  low  supports,  as  far  apart 
as  they  will  be  in  bridge;  as  many  men  as  can  then  step  on  it 
and  jump  up  and  down;  or  It  is  otherwise  arranged  so  as  to 
bring  as  great  a  weight  upon  it  as  It  will  have  to  bear  at  any  time 
in  bridge. 

Where  small  poles  of  the  usual  number  would  not  be  strong 
enough,  a  greater  number  must  be  used  until  the  desired  strength 
is  gained. 

250.— Transoms  must  be  strong  enough  to  bear  all  the  weight 
that  may  be  brought  upon  one  bay  of  the  bridge,  considered  as 
distributed  dead  load  on  the  transom. 

251.— T/?c  load  in  pounds  which  any  timber  resting  on  two 
points  of  support  will  safely  bear,  concentrated  at  its  center,  may 

be  approximately  determined  by  the  formula  1-3  x  -p  x  O,  in 
which  b  =  the  breadth  in  inches,  d  =  the'  depth  in  inches,  1  =  the 
length  in  feet  between  supports,  and  C  is  a  constant  in  pounds  for 
the  particular  material  of  the  beam.*  1-3  Is  the  fraction  of  the 

*C  is  determined  by  takine^  a  piece  1  in.  square  and  1  ft.  longbetween  supports, 
loading-  it  at  the  center  until  it  breaks,  then  to  the  applied  load  adding  one-half 
the  weight  of  the  piece  between  supports,  and  the  sum  will  be  C;  or.  a  piece  of 
any  convenient  size  and  length  can  be  used,  afterwards  deducing  what  the 
breaking  weight  would  be  for  a  piece  1  in.  square  and  1  ft.  long,  remembering 
that  the  breaking  weight  varies  directly  with  the  width,  as  the  square  of  the 
depth,  and  inversely  as  the  length. 


PLATK  35. 


jg£fil 


Spar  Bridges.  121 

breaking  weight  used  for  safety.  It  would,  in  all  cases,  be  better 
to  use  a  smaller  fraction  of  the  breaking  weight,  as  1-5  or  1-6;  or 
even  1-8  in  structures  designed  to  be  of  a  lasting  character.  The 
formula  is  for  a  rectangular  beam,  but  for  a  cylindrical  timber 
whose  mean  diameter  equals  the  side  of  a  square  beam,  use  6-10 
of  what  the  formula  gives. 

252.— Weight  brought  on  a  hridge  by  the  passage  of  troops,  taken 
as  distributed  live  load  for  Infantry  and  Cavalry:  Infantry  in 
column  of  twos  or  fours,  about  225  lbs.  per  lineal  foot.  Infantry 
when  crowded  at  a  check  in  fours,  about  550  lbs.  per  lineal  foot. 
Cavalry  in  column  of  twos,  about  230  lbs.  per  lineal  foot.  Cavalry 
when  crowded  at  a  check,  about  350  lbs.  per  lineal  foot.  When 
Artillery  carriages  cross  a  bridge,  the  weight  is  not  equally  distrib- 
uted, but  is  greatest  when  the  wheels  bearing  the  heaviest  load  are  on 
the  center. 

253.— A  uniformly  distributed  dead  load  produces  only  one- 
half  the  strain  of  an  equal  dead  load  concentrated  at  the  cen- 
ter. A  moving  or  live  load  produces  twice  the  strain  of  a  dead 
load.  A  uniformly  distributed  live  load  equals  a  concentrated 
dead  load. 

Table  of  Constants  C,  for  finding  the  breaking  load  of  various 
materials  by  the  formula^x-pxC  when  concentrated  at  cen- 
ter of  beam  supported  at  both  ends.  From  Trautwine's 
"Engineer's  Pocket  Book": 

Ash,  white 650  Elm 350   Oak,  red  &  black..550 

Ash,  swamp 400  Hemlock 400  Pine,  white 450 

Ash,  black 300  Hickory 700   Pine,  yellow 500 

Beech,  white .450  Hickory,  pig  nut. 500   Pine,  pitch 550 

Beech,  red 550  Locust 600  Poplar 550 

Birch, 450  Mahogany 450  Spruce 450 

Cedar 250  Maple 550  Sycamore 500 

Chestnut 4.50  Oak,  white  &  live.600  Walnut 450 

254:.— The  cubic  contents  of  a  log  is  appioximately  equal  to 
0.7854  times  the  square  of  the  mean  diameter  times  the  lengfh, 
or  the  area  of  the  mean  section  multiplied  by  the  length;  or  the 
square  of  one-fifth  the  mean  circumference  times  twice  the  length, 
all  in  feet. 

255.— In  calculating  the  strength  of  a  round  timber  or  spar, 


122  Spar  Bridges. 

its  mean  diameter  is  used,  because  such  a  spar,  if  overloaded,  will 
break  at  center,  instead  of  at  small  end.* 

256.— The  following  table  gives  the  weights  in  pounds  per 
cubic  foot  of  various  materials: 

Iron,  cast 450  Chestnut  40  Spruce 31 

Iron,  wrought 487  Cottonwood 35  Sycamore 37 

Lead 710  Hicliory 43-49  Walnut ,  .38 

Steel 488  Maple 48  Clay  .120 

Ash 38-47  Oal£ 45-60  Earth 72-120 

Cedar 35  Pine  34-40  Gravel  &  sand..90-130 

Green  timbers  weigh  from  1-5  to  1-2  more  than  those  in  table. 

257.— When  spars  are  used  for  ballis,  they  must  be  arranged 
so  as  to  have  alj  butts  or  all  tips  together  on  a  transom.  They 
should  have  good  overlap  and  be  well  lashed  to  each  other  and  to 
the  transoms.  To  allow  for  settling,  the  center  is  generally  made 
higher  by  about  1-30  the  span. 

258. — Stringer  Bridge.  For  spams  of  25  ft.  or  less,  if  timber  is 
available,  the  simplest  form  of  stringer  bridge  could  be  built,  as  in 
Fig.  2,  of  6  balks,  30  ft.  long,  reaching  clear  across,  covered  with 
small  poles  4  to  6  in.  in  diameter,  12  ft.  long,  for  a  floor.  Side-rails 
would  be  laid  on  the  floor  over  the  outside  balks  and  either  lashed 
or  pinned  to  the  balks.  Hand-rails  would  be  as  shown,  or  a  rope 
stretched  across  would  answer.  Time  of  construction — 1  hour.  The 
balks  could  be  jumped  across  as  shown  in  either  Figs.  3  or  4. 

259. — Scarped  Bridge.     If  stringers  of  length  to  reach  across 

*For  a  bridee  constructed  as  in  Fig.  2,  with  six  balks,  to  determine  the  safe 
load  it  will  carry,  the  application  will  be  about  as  follows: 

The  balks  being  of  ^-ellow  pine,  ""O  in  in  diameter  at  fhe  center,  25  ft.  be- 
tween supports,  the  formula  gives  yV  X  g^  X  ^%^  x500  =  4,000  lbs.  as  the  safe  load 
each  balk  will  bea^-  concentrated  at  the  center,  including  its  own  weight.  Cal- 
culating for  five  balks,  on  the  supposition  that  the  two  outside  ones  receive  only 
one-half  the  strain  of  the  center  ones,  they  will  bear  5  x  4,000  lbs.  =  20,000  lbs. 
f  oncentrated  at  center.  From  this  deduct  half  the  weight  of  the  balks  and  floor 
concentrated  at  center,  found  by  multiplying  one-half  the  cubic  contents  by  the 
weight  per  foot;  for  the  six  balks  this  will  be 

6  X  H  fP)'  X  .7854]  X  25  x  40  =  1,636.25  lbs. 
For  the  floor  of  seventy-five  4-in.  poles,  each  12  ft.  long,  the  weight  will  be 
75  X  *  X  [  (^^2  x  .7854]  x  12  x  40=  1,570.86  lbs 

20,000  lbs.  — 3,207.11  lbs.  --  16.792.89  lbs.,  the  capacity  of  the  bridge  concentrated  at 
the  center.  Infantry  niarchine:  in  column  of  fours  crowded  by  a  check  would 
cause  a  load  of  onlyabout  13,750  lbs.  Cavalry  in  column  of  twos  crowded  by  a 
check  only  about  8,750  lbs. 

Similarly,  knowing  the  span,  the  kind  of  material  at  hand,  the  weight  to  be 
borne,  etc.,  the  size  of  timbers  required  can  be  deduced;  or,  having  the  size  and 
kind  of  the  timbers,  weight  to  be  borne,  etc.,  the  greatest  length  that  can  be 
spanned  can  be  determined  by  the  above  formula. 


PLATE  36. 


124  Spar  Bridges. 

cannot  be  obtained  or  are  too  heavy  to  handle  easily,  a  scarped 
bridge  as  in  Fig.  5  might  be  made,  requiring  only  axes  and  augers. 
The  shore  stringers,  25  ft.  long,  10  in.  in  diameter,  six  on  each 
shore,  have  their  bridge  ends  scarped  on  upper  side  18  in.,  then 
pushed  out  10  ft.,  their  shore  ends  being  well  anchored  down  and 
loaded  with  roadway.  Six  short  stringers,  8  ft.  long,  10  in.  in  diam- 
eter, three  on  each  shore,  scarped  18  in.  on  under  side  of  each  end, 
are  passed  over  gap  and  laid  on  shore  stringers.  Two  2-in.  auger 
holes  are  bored  at  each  end  through  both  stringers  and  wooden 
pins  driven  through,  and  the  flooring  completed. 

260.— Paine's  Bridge.  (Fig.  6.)  If  timber  is  abundant  and 
stream  not  over  6  ft.  deep,  select  trees  up  stream.  Fell,  and  trim 
off  branches.  Bore  two  3-in.  auger  holes  near  butt  ends  3  in.  apart, 
making  an  angle  of  30°  with  each  other,  and  a  third  hole,  making 
an  angle  of  45°,  between  them  nearer  the  butt.  Cut  and  insert  in 
outside  holes  legs  long  enough  to  raise  the  butt  the  desired  height 
of  bridge.  Float  down  stream,  butt  end  first,  to  position  of  bridge. 
On  arriving  in  line  of  bridge,  the  log  is  turned  on  its  feet,  the  tip 
sinking  to  bottom.  The  brace  leg  is  then  inserted  down  stream 
in  last  hole,  making  an  angle  of  45°.  Log  after  log  is  thus  placed, 
balks  rolled  up  and  put  into  position  and  leveled,  and  the  floor  laid 
in  the  usual  way. 

261. — Trestle  Bridges.  For  spans  of  25  ft.  or  over,  when  bot- 
tom can  be  touched  clear  across,  some  form  of  trestle  bridge  will  be 
the  easiest  of  construction. 

262.— The  Six-legged  Trestle.  In  PI.  36,  Fig.  1,  the  trestle  con- 
sists of  6  legs,  4  vertical  and  2  inclined;  the  two  vertical  legs  on 
each  side  are  fastened  to  two  short  sills  by  2-in.  pins.  The  ends  of 
the  two  inclined  legs  are  cut  on  an  angle,  driven  into  position,  and 
held  by  2-in.  pins  passing  through  the  transom  from  above.  They 
serve  as  braces  and  supports.  A  short  horizontal  piece  pinned  to 
each  pair  of  vertical  legs  supports  the  transom,  which  is  also 
pinned.  On  top  of  the  projecting  ends  of  the  vertical  legs  a  cap 
piece  can  be  pinned  to  form  hand-rails.  The  trestle  is  made  on 
shore,  floated  to  its  place  in  bridge,  and  erected  with  the  aid  of  a 
float  held  at  the  proper  distance  from  last  trestle  by  a  pole  on  each 
side,  having  the  lengths  of  the  spans  marked  by  pins  which  engage 
the  transoms  of  the  trestles.  The  transoms  are  only  temporarily 
lashed  in  position  at  first,  but  after  the  trestle  is  erected  in  its 


^par  Bridges,  125 

proper  place  the  proper  height  for  it  is  determined  by  bringing 
the  2  distance  poles  horizontal,  or  a  little  above  the  horizontal  if 
a  camber  is  to  be  given,  then  pinning  or  spiliing  on  the  short  hori 
zontal  pieces.  If  accurate  soundings  have  been  made  across  the 
stream  on  the  lines  of  the  legs  of  the  trestles,  then  the  trestles  can 
be  completed  on  shore  before  launching.  The  balks  are  then 
run  across  and  pinned  and  roadway  finished.  If  there  occurs 
unequal  settling,  the  roadway  can  be  raised  by  blocking  up  under 
the  transoms  on  the  short  horizontal  pieces. 

263. — The  Tie-block  Trestle.  Fig.  2  is  another  form  of  tres- 
tle, consisting  of  only  two  legs,  about  8  in.  in  diameter. 
The  transoms  are  in  pairs,  across  which  two  blocks  are  spiked  at 
each  end  into  notches,  as  shown.  This  trestle  can  be  used  on 
hard,  uneven  bottom.  The  trestle  is  formed  on  shore,  held  in 
shape  by  the  rope,  and  rack  stick  across  the  top,  then  floated  into 
place.  Two  poles,  longer  than  two  spans,  are  then  run  out;  on  the 
projecting  ends  are  pins  to  prevent  the  trestle  slipping  off,  and  on 
near  end  a  rope  for  fastening  to  transoms  of  second  trestle  back. 
Having  caught  the  trestle  on  the  ends  of  the  poles  under  the 
transom,  it  can  be  raised  to  a  vertical  position  by  men  bearing 
down  on  the  rear,  and  held  by  means  of  ropes;  it  is  then  lowered 
into  position,  legs  in  a  vertical  plane.  The  transoms  are  then 
adjusted  to  their  proper  elevation  by  striking  on  under  side,  if 
too  low,  then  tightening  rope;  or  by  slackening  the  rope  and  strik- 
ing on  upper  side  if  too  high. .  When  properly  adjusted,  the  rope  is 
tightened,  pinching  the  legs  between  the  blocks;  the  braces  are 
then  spiked  or  pinned  on,  the  rope  removed,  the  balks  laid  and 
pinned,  and  the  poles  shoved  out  for  the  next  trestle. 

264. — The  Four-legged  Capped  Trestle.  Where  sufficient  lum- 
ber can  be  procured,  the  most  expeditious  and  probably  the  best 
method  will  be  as  follows:  (Pig.  3.)  With  the  balks  and  chesses 
for  each  span,  form  a  raft,  or  as  many  as  may  be  desired, the  length 
of  a  span.  Form  a  trestle  by  placing  four  legs  parallel  and  4  ft. 
apart  from  center  to  center.  Spike  a  pole  across  near  the  bottom 
and  ono  near  the  top  to  keep  them  together.  The  first,  or  any  tres- 
tle, having  been  set,  float  a  raft  against  it  and  make  fast;  bring  the 
trestle  to  be  set  up  to  the  other  end;  force  the  legs  under  the  raft  a 
distance  a  little  less  than  the  depth  of  the  water.  Tie  a  rope  around 
the  outside  legs  at  **f"  with  a  bow-knot,  to  hold  from  slipping  un- 


126  Spar  Bridges. 

der,  ana  others  to  the  top  pole,  by  means  of  which  it  is  raised  to  a 
vertical  position,  when  it  is  dropped  to  the  bottom  by  slackening 
off  on  lower  ropes.  As  soon  as  it  is  dropped,another  raft  is  brought 
up,  tied,  and  another  trestle  put  into  position,  and  so  continued. 
Each  trestle,  as  soon  as  it  is  in  position,  is  then  capped  by  nailing 
two  boards  horizontally  on  opposite  sides  of  legs  with  tops  in  same 
plane.  (Fig.  3,  a.)  Braces  arie  then  spiked  on  the  legs.  Saw  off  the 
two  inside  posts  even  with  the  tops  of  boards.  Spike  a  2-in.  plank 
across  the  top  of  posts  and  boards.  Lay  the  balks,  spike  them, 
remove  the  raft,  and  move  it  into  position  to  raise  another  trestle. 
If  boards  cannot  be  procured  for  capping,  round  sticks  may  be 
used  as  in  Fig.  3,  b,  by  cutting  the  two  inside  legs  off  5  or  6  in. 
above  the  horizontal  poles,  then  spiking  two  short  pieces  across 
the  poles  against  the  outside  legs  and  one  in  center  on  which  the 
cap  piece  or  transom  will  rest.  Advantages  are — work  can  be 
commenced  in  any  number  of  places  at  the  same  time;  no  accu- 
rate soundings  required  so  long  as  poles  are  sufficiently  long;  cap- 
ping and  bracing  do  not  retard  work;  different  squads  can  be  at 
work  at  same  time,  etc. 

265. — The  Two-legged  Trestle.  If  only  axes  and  rope  are 
available,  trestles  may  be  made  by  lashing  their  parts  together. 
(Fig.  4.)  Having  determined  the  height  of  the  roadway  above 
the  bottom  of  the  stream,  mark  this  height  from  the  butts  on 
both  leg;s,  then  mark  the  position  of  the  transom  on  the  legs, 
allowing  for  the  thickness  of  the  balks;  also  mark  on  the  transom 
the  width  of  roadway  between  side-rails  plus  3  ft,  for  points 
of  crossing  of  legs,  the  distance  apart  of  legs  depending  on 
width  of  roadway.  Give  the  legs  a  splay  outwards  at  the  bottom 
of  1-6  and  mark  on  legs  and  ledger  the  points  of  lashing.  All  be- 
ing ready,  lay  the  transom  on  a  couple  of  supports  3  or  4  In.  high, 
inside  the  position  of  the  legs,  lay  on  the  legs  in  their  proper  posi- 
tions, on  the  legs  lay  the  ledger.  With  the  square  lashing  fasten 
the  four  points  of  crossing.  Next,  lay  on  the  braces,  butts  and 
one  tip  on  same  side  as  ledger  and  one  tip  on  side  of  transom. 
Lash  the  butts  with  square  lashings.  Square  the  trestle  by  mak- 
ing the  diagonals  equal,  measuring  from  the  center  of  ledger  lash- 
ing on  one  leg  to  the  center  of  transom  lashing  on  opposite  leg. 
When  these  diagonals  are  made  equal  the  tips  are  lashed  with 
square  lashings  and  the  braces  at  the  middle  with  a  cross  lash- 


Spar  Bridges.  127 

iiig.  Ledger  and  braces  can  be  of  ratlier  light  timber.  Tlie  tres- 
ues  can  be  floated  into  position  and  raised  as  already  described, 
or  run  out  and  down  from  the  end  of  the  bridge,  which  is  more 
difticult.  They  are  kept  vertical  by  lashing  the  balks  to  the 
transoms,  and  longitudinal  bracing  from  one  to  another. 

266.— A  Three-legged  Trestle  (ri.  37,  Fig.  1)  may  be  made 
by  first  lashing  two  legs  together  considerably  higher  than  the 
roadway  is  to  be,  then  lashing  the  pry -pole  just  below  to  one  of 
the  legs,  all  with  shear  lashings.  Stand  the  trestle  up,  spread 
out  legs  till  butts  rest  on  the  vertices  of  an  equilateral  triangle 
whose  sides  are  ^>  height  of  trestle,  then  lash  three  light  ledgers 
to  the  legs  by  round  lashings.  On  the  outside  of  the  pry-pole 
and  leg  to  which  it  is  fastened  are  lashed  short  pieces,  by  square 
lashings,  on  which  rest  two  longer  pieces,  separated  by  the  legs, 
which  are  lashed  together  by  the  shear  lashing.  On  these  longer 
pieces  rest  the  transoms.  With  these  trestles  lighter  material 
can  be  used;  they  stand  without  bracing,  but  are  difficult  to  place; 
accommodate  themselves  to  inequalities  of  surface;  the  roadway 
may  be  readily  raised  or  lowered.  If  material  is  available,  they 
are  readily  made  with  spikes. 

267.— The  Four-legged  Trestle,  second  form.  (Fig.  2.)  Two 
two-legged  trestles  are  made,  one  being  12  to  18  in.  narrower  than 
the  other,  depending  on  the  size  of  legs,  so  that  they  will  lock  when 
put  together.  The  transoms  are  placed  on  same  side  as  ledgers, 
instead  of  on  opposite  sides.  The  butts  of  the  single  trestles  are 
placed  a  distance  apart  equal  to  half  the  height,  then  locked  at 
the  top,  the  transoms  lashed  at  the  ends,  longitudinal  braces 
lashed  at  the  ledgers,  the  tips  tied  and  racked  together.  Some- 
times used  with  light  material,  also  as  steadying  points  in  a  long 
bridge  of  two-legged  trestles.  One  similar  to  it  can  be  made  of 
sawed  timber  and  spikes  and  placed  in  position  as  shown  in  Figs. 
3  and  4,  if  the  materials  are  available. 

26S. — Crib  Piers.  In  sluggish  streams  with  muddy  bottoms  an.i 
not  over  6  ft.  deep,  where  timber  is  abundant,  crib  piers  may  be 
used.  (Fig.  5.)  The  cribs  are  built  in  the  woods,  the  foundation 
logs  being  pinned  together,  the  others  simply  notched.  The  logs 
then  marked,  taken  down,  carried  or  floated  into  position,  and  re- 
built, poles  being  generally  set  to  mark  the  corners.  As  the  crib 
is  built  up  it  gradually  sinks,  or  a  tray  may  be  formed  Inside  and 
loaded  with  stones.  The  balks  and  flooring  are  laid  as  usual. 
9 


FLATS  3!? 


FLAtli  38. 


FIG.l. 


FIG.  4.  Single  Lock  . 


ab  must  not  bo  less  tkani  Op  cd 


Ji^ 


^^0  Spar  Bridges. 

269.— rUa  bridyas  are  scarcely  adapted  to  an  emergency,  from 
the  time  and  preparation  required  in  tlieir  construction,  but  on 
lines  of  communication,  from  tlie  ciiaracter  of  tlie  bottonl  or  the 
dangers  from  floating  objects,  resort  may  be  had  to  them. 

J270.— For  driving  the  piles,  a  monkey  (Fig.  8)  is  made  of  a 
block  of  wood  3  ft.  long,  12  in.  in  diameter,  with  four  1.5  in.  pins 
at  top  and  four  on  the  sides  for  handles.  --ur  men  standing  on 
a  platform  on  the  pile  drive  it  down,  their  own  weight  thus  assist- 
ing, or  they  may  be  driven  from  a  raft  built  as  in  Fig.  6.  After 
the  piles  are  driven  they  are  straightened,  braced,  their  tops  sawed 
off  level,  the  caps  placed  on  and  pinned  (PI.  38,  Fig.  1),  and  the 
roadway  laid  as  usual.  Piles  near  shore  may  be  driven  as  in  Fig.  7. 

271.— For  crossings  greater  than  25  ft.  and  too  deep  to  use  any 
of  the  above  forms,  resort  must  be  had  to  some  form  of  truss 
bridge.  The  trusses  may  be  put  together  either  by  lashing  or 
with  pins,  or  by  combinations  of  both.  \ 

272.— PI.  38,  Fig.  2,  represents  the  ordinary  King-post  Truss 
for  spans  up  to  40  ft.  The  bridge  is  put  together  on  the  bank, 
then  pushed  forward  half  its  length,  using  rollers  under  each 
truss,  as  shown.  A  trestle  is  then  leaned  forward  from  opposite 
bank,  and,  when  truss  is  over  It,  the  trestle  is  raised  and  the  end 
of  the  truss  carried  over  to  the  opposite  bank. 

273.— Fig.  3  represents  the  Queen-post  Truss  for  spans  up 
to  50  ft.  It  is  constructed  and  carried  across  similarly  to  the  pre- 
ceding one. 

274.— Fig.  4  shows  the  Single  Lock  for  spans  of  30  ft.  It  con- 
sists of  two  frames  similar  to  the  two-legged  trestle  on  PI.  36, 
Fig.  4.  A  section  of  the  gap  is  first  marked  out  on  the  ground  on 
each  bank  with  the  positions  of  the  footings  indicated.  On  these 
the  legs  are  laid  and  the  positions  for  lashing  the  transoms  and 
ledgers  marked.  The  frames  are  then  put  together  opposite  the 
position  they  are  to  occupy  (one  on  each  bank),  butts  towards  the 
gap.  One  frame  is  made  15  to  18  in.  wider  than  the  other  so  they 
will  lock,  and  the  footings  should  be  likewise  prepared.  The  dis- 
tance between  legs  at  transom  of  narrower  frame  Is  at  least  18  in. 
more  than  width  of  roadway  between  side-rails.  With  the  above 
exceptions,  the  frames  'are  made  like  the  two-legged  trestles.  The 
splay  of  the  legs  Is  very  slight,  generally  about  1  ft.  between  tran- 
som an  I  ledger.    Stout  stakes  are  then  driven  at  the  rear,  fore  and 


Spar  Bridges.  131 

back  guys  are  attached  to  the  tips  of  each  frame,  the  fore  guys 
crossed  over  the  stream,  those  of  narrower  frame  in  center.  Foot 
ropes  are  also  attached  to  each  leg  near  the  butts  with  timber 
hitches  and  a  turn  taken  around  the  stakes  at  the  rear.  The  frames 
are  then  shoved  over  the  banks  till  they  balance  (PI.  40,  Fig.  1), 
then  brought  to  a  vertical  position  by  hauling  on  the  fore  guys, 
and  lowered  into  their  places  by  easing  off  on  the  foot  ropes, 
after  which  they  are  pulled  over  and  locked.  A  couple  of  balks 
are  then  run  out,  then  the  fork  transom  is  put  into  place  and  the 
balks  rested  on  it.  The  remainder  of  the  balks  are  then  run  out, 
placed  on  the  fork  transom,  lashed,  and  the  roadway  completed 
as  usual.  If  good  places  for  footings  cannot  be  secured,  then 
other  means  must  be  provided. 

275.— i^or  spcms  up  to  45  or  50  ft.,  the  Double  Lock  (PI.  39, 
Fig.  1)  may  be  used.  In  this  it  will  be  noticed  that  the  balk- 
bearing  transoms  are  not  the  transoms  first  lashed  to  the  frames 
In  making  them,  but  those  which  are  sent  out  after  the  frames 
are  in  position.  This  must  be  remembered  in  marking  the  posi- 
tions of  the  transoms  on  the  legs  of  the  frames.  In  this  the 
two  frame?  are  made  as  described  for  tTie  single  lock,  except  that 
they  are  of  the  same  width.  They  are  launched  as  described, 
and  pulled  forward  until  their  tops  are  about  1-3  the  span  apart. 
Two  straining  beams  are  then  run  across,  the  road-bearing  tran- 
soms fastened  on  top  of  them  in  the  positions  previously  marked. 
The  frames  are  held  by  the  back  guys  until  all  is  ready,  when 
they  are  eased  off  and  the  bridge  locked.  The  roadway  is  then 
laid  as  usual. 

27Q.—For  spans  greater  than  45  or  50  ft.,  where  timber  of  suffi- 
cient size  is  obtainable,  the  Single  Sling  or  Treble  Sling  may  be 
used.  The  frames  are  made  as  has  been  described,  with  the  fol- 
lowing additional  observations: 

In  the  Single  Sling  (Fig.  2),  in  marking  the  positions  of  the  dif- 
ferent spans,  the  three  locking  pieces  must  be  at  least  9  or  10  ft. 
above  the  roadway.  The  fork  piece  is  hauled  into  position  by 
snatch  blocks  lashed  to  the  top  of  each  leg  of  narrower  frame, 
after  which  the  blocks  are  used  to  get  the  center  transom  tempo- 
rarily Into  position,  when  It  Is  slung  by  the  ropes  that  are  to  hold 
It,  by  taking  several  turns  around  It  and  the  locking  pieces  with- 
out riding,  and  afterwards  twisted  up  to  the  proper  heljrht  with 
a  pole. 


PLATE   39. 


Double  Lock 


Straining  bear^i 


T.  T    Road  bearing  transarM 
45  pn, 

Plgl. 


PLATE  4^. 


_  -^. 


FIG.  5 


134  Spar  Bridges. 

277.— In  the  Treble  Sling  (Fig.  3)  there  are  three  slung  tran- 
soms, one  from  th^  forks  and  one  from  the  standards  on  each  side 
of  the  middle.  The  frames  are  constructed  as  ah-eady  described 
(PI.  40,  Fig.  2,  being  one  in  plan.)  If  necessary,  the  frames  may 
be  strengthened  by  additional  braces  on  them  and  further  braced 
back  to  the  banks  by  ropes  attached  to  holdfasts  and  otherwise 
as  suggested  on  PL  40,  Figs.  4  and  5,  vertical  braces  being  shown 
in  Fig.  3. 

278.— Other  expedients  for  crossing  small  gaps  are  the  use  of 
wagons  in  various  ways  for  supports,  brushwood  made  Into 
gabions,  fascines,  etc.    (Figs.  6  and  7.) 

279.— A  light,  portable  truss  (Fig.  11)  can  be  made,  where 
boards  are  obtainable,  by  describing  two  arcs  of  circles  with 
radii  151  ft.,  on  opposite  sides  of  a  60  ft.  chord,  then  driving 
stakes  on  the  arcs  at  intervals  of  about  2  ft.,  against  which  5 
layers  on  top  and  6  layers  on  bottom  of  boards  1  in.  thick  x  12 
In.  wide,  breaking  joints,  are  bent  and  securely  nailed  together 
every  4  in.  with  tenpenny  nails.  The  lower  side  of  truss  is  made 
gne  board  thicker  than  the  upper  and  is  completed  by  driving 
6  in.  spikes  througli  every  6  in.  This  truss  will  be  about  6  ft. 
deep,  and,  allowing  2  ft.  at  each  end  for  resting  on  supports,  will 
bridge  a  span  56  ft. 

The  sides  are  connected  every  5  or  6  ft.  by  vertical  pieces'  of 
plank  and  two  1-in.  iron  rods,  the  latter  on  the  sides  of  the  verti- 
cals, towards  the  middle.  If  iron  rods  are  not  obtainable,  rope  or 
wire  should  be  wrapped  around  both  and  twisted  tightly.  The 
angles  at  the  ends  are  filled  with  wedge-shaped  pieces  and  the 
ends  securely  bolted,  hooped,  or  wrapped.  (Fig.  9.)  For  greater 
rigidity,  light  diagonal  braces  may  be  inserted  in  the  panels. 
The  top  can  be  made  straight  instead  of  curved  if  so  desired. 

These  trusses  are  used  in  pairs  and  are  applicable  to  a  variety 
of  structures  and  to  spaces  of  considerable  width.  Two  such 
trusses  with  a  central  support  of  trestles,  crib- work,  or  boats,  may 
be  used  for  116  ft.  (Fig.  11);  three  such  trusses  for  176  ft.,  etc. 
In  experiments  with  such  trusses  in  bridges,  1800  lbs.  per  lineal 
foot  has  been  applied  before  breaking;  and  by  covering  the  boards 
with  pitch  and  tar  before  nailing  together,  inserting  %  In.  bolts 
in  pairs  every  foot  of  length  on  lower  side,  and  nailing  boards 
against  the  edges,  3500  lbs.  per  lineal  foot  was  applied  before 
breaking. 


Spar  Bridges.  135 

280.— Suspension*  Bridges.  For  spans  greater  than  60  ft.. 
and  when  timbers  for  frames  cannot  be  procured,  some  form  of 
suspension  bridge  might  be  used.  Although  applicable  to  longer 
spans,  and  the  materials  more  easily  transported,  they  take  longer 
to  make  than  other  kinds. 

The  cables  may  be  of  iron  chains,  iron,  steel  or  fibrous  ropes, 
or  of  boards  nailed  together. 

281.— PI.  40a,  Fig.  1,  shows  one  with  the  roadway  hung  below 
the  cables,  with  a  camber  1-30.  At  the  center,  the  roadway 
should  be  at  least  1  ft.  below  the  cables.  The  width  of  roadway 
between  side  rails  should  be  only  slightly  wider  than  wagon-wheel 
tracks.  (Fig.  2.)  On  the  banks,  the  cables  are  supported  by  tim- 
ber piers  (Fig.  3),  having  a  broad  cap  (Fig.  4),  rounded  on  top, 
over  which  they  pass  at  a  distance  apart  of  9.5  ft.  The  cables 
must  be  securely  anchored  at  the  rear  to  heavy  logs  sunk  4  or  5 
ft.  in  the  ground,  or  otherwise,  and  drawn  in  until  the  sag  is  only 
1-10  pr  1-12  of  the  span. 

282.— In  Fig.  5,  part  of  the  roadway  is  hung  below  and  a  part 
rests  on  the  cables,  the  greatest  slope  of  road  being  1  on  6  for  100 
ft.  span  and  1-10  sag.    The  cables  are  only  7  ft.  apart. 

283.— In  Fig.  6,  the  roadway  is  built  on  trestles  supported  on 
the  cables.  For  spans  130  ft.  sag  1-12,  the  frames  form  the  sides 
of  equilateral  triangles  of  10  ft.  each.  To  construct  it,  the  curve 
of  the  cables  is  traced  on  the  ground,  the  trestle  legs  laid  on  it  and 
marked  where  they  cross  the  road  and  cable;  those  for  each  half 
of  the  bridge  are  ranged  in  order  on  the  banks,  connected  together 
as  placed  on  the  cables  and  hauled  out,  connected  at  the  center, 
the  curve  of  the  cables  adjusted  and  the  bridge  completed. 

284.— Fig.  7  is  a  suspension  bridge  of  which  the  cables  are 
made  of  boards  nailed  together  in  several  thicknesses  laid  hori- 
zontally, breaking  joints;  the  ends  are  spread  apart  and  wedge- 
shaped  blocks  inserted  and  anchored  by  several  rows  of  posts,  as 
shown  in  Fig.  8.  Each  cable,  as  made,  is  drawn  across  by  ropes, 
anchored,  and  the  trestles  placed  from  both  ends  at  the  same 
time.  Last  of  all,  spikes  long  enough  to  reach  entirely  through 
the  cable  are  driven  every  4  to  6  in. 

285.— Fig.  11  is  a  similar  bridge  supported  on  trestles  16  ft. 
long,  not  exceeding  20  ft.  high,  placed  at  intervals  of  40  ft.,  over 
which  suspends  the  two  board  cables,  14  ft.  apart.    On  these  are 


PUTE  40a. 


Spar  Bridges.  137 

placed  low  trestles,  3  ft.  high,  dividing  the  spans  into  lengths  of 
20  ft.  each;  25  ft.  balks  are  used  and  the  roadway  laid  as  usual. 
The  cables  are  made  of  six  thicknesses,  of  1  in.  boards  12  in. 
wide,  breaking  joints,  nailed  and  spiked  every  4  to  6  in.,  and  bolt- 
ed by  pairs  of  %  in.  bolts  every  foot.  Three  thicknesses  of  boards 
are  first  nailed  together  and  drawn  across,  the  ends  anchored,  and 
then  the  other  three  boards  added. 

286.— For  light  foot  bridges  (Fig.  10),  across  narrow  gaps,  wire 
from  fences,  if  available,  could  be  used  for  the  cables  by  twisting 
a  number  together  and  passing  them  over  crotches  of  trees  and 
anchoring  to  stumps,  etc.,  in  rear,  and  then  laying  the  walk  simi- 
lar to  some  of  the  methods  previously  shown. 

287.— So  various  are  the  conditions  to  be  met  in  constructing 
bridges  that  seldom  will  any  one  type  meet  the  requirements,  but 
by  the  application  of  good  judgment  and  resource,  with  the  sug- 
gestions here  offered,  almost  any  gap  of  reasonable  width  may  be 
crossed,  if  not  by  one  type  or  another,  then  by  a  combination  of 
several  to  meet  the  emergency. 

The  varying  strength  of  timbers  makes  it  almost  impossible  to 
give  exact  dimensions  for  the  different  spars  to  be  used  in  the 
different  types,  but  a  general  idea  may  be  obtained  below  of  the 
amounts  and  average  dimensions  of  medium  strength  timber,  as 
yellow  pine.  For  weaker  timbers  some  of  the  sizes  will  have  to 
be  increased,  while  for  stronger  ones  there  will  be  an  excess  of 
strength  if  the  sizes  given  are  adhered  to,  but  the  desire  to  be  on 
the  side  of  safety  warrants  the  use  of  amounts  which  might,  by  a 
careful  mathematical  calculation,  appear  to  be  excessive. 

The  timbers  for  transoms,  ledgers,  braces,  balks,  flooring  and 
side  rails  should  be  selected  of  as  nearly  a  uniform  diameter 
throughout  as  possible  and  will  be  so  considered  in  giving  dimen- 
sions.   For  legs  or  standards  the  diameter  at  tip  will  be  given. 

For  a  9  ft.  roadway  with  15  ft.  spans,  5  balks  20  ft.  long  x  about 
6  in.  in  diam.  are  used,  and  placed  2^  ft.  apart  from  center  to  cen- 
ter. For  the  flooring  are  used  poles  11  to  12  ft.  long  x  4  to  5  in. 
in  diam.    For  side  rails  2  poles  20  ft.  long,  4  to  6  in.  in  diam. 

For  each  Six-legged  Trestle  (PI.  36,  Fig.  1)  4  vertical  and  2 
bracing  legs  6  in.  diam.;  1  transom  12  ft.  x  8  in.;  2  foot  pieces  3  ft. 
X  8  in.;  10  oak  pins  2  in.  diam. 

For  eacli  Tie-block  Trestle  (Fig.  2)  2  legs  8  in.  d!am.;  2  tran- 


138  Spar  Bridges. 

soms  15  ft.  X  8  in.;  4  tie  blocks  2  ft.  x  5  in.  x  6  in.;  2  braces  3  ft.  x 

2  in.  X  6  in.;  24  spikes,  1  rope,  1  rackstick. 

For  each  Capped  Trestle  (Fig.  3)  4  legs  8  in.  diam.;  2  braces 
12  ft.  X  4  in.;  2  braces  15  ft.  x  5  in.;  3  boards  12  ft.  x  2  in.  x  12  in.; 
4  ropes,  spikes. 

For  each  Two-legged  Trestle,  lashed  (Fig.  4),  2  legs  4  ft. 
longer  than  height  of  trestle,  5  to  7  in.  tip;  1  transom  15  ft.  x  9  in.; 

1  ledger  16  ft.  x  4  to  6  in.;  2  braces  3  to  5  in.  diam.;  6  ropes  30  ft.  x 
^  in.  diam.;  3  ropes  15  ft.  x  %  in.  diam. 

For  each  Three-legged  Trestle,  lashed  (PI.  37,  Fig.  1),  6  legs  3 
to  5  in.  tip;  4  transom  bearers  6  ft.  x  3  to  4  in.;  4  sticks  2  ft.  x  2  to 

3  in.;  6  ledgers  2  to  3  in.  diam.;  1  transom  15  ft.  x  9  in.;  12  ropes 
30  ft.  X  ^  in.  diam.;  6  ropes  15  ft  x  i^  in.  diam. 

For  each  Four-legged  Trestle,  lashed  (Fig.  2),  twice  the 
amount  given  for  each  two-legged  trestle,  plus  2  ledgers,  and  6 
lashings  15  ft.  long. 

For  each  Single  Lock  (PI.  38,  Fig.  4)  4  legs  22  to  25  ft.  x  7 
in.  tip;  1  fork  transom  15  ft.  x  10  in.;  2  frame  transoms  15  ft.  x  6 
in.;  2  ledgers  15  ft.  x  4  to  6  in.;  4  braces  20  ft.  x  3  in.;  2  shore  sills 
15  ft.  X  6  in.  LasMn{/s,  4  transom  50  ft.  x  ^  in.;  14  ledger  and 
brace  30  ft.  x  %  in.;  10  balks  20  ft.  x  1-3  in.;  4  foot  50  ft.  x  1  in.;  8 
guy  150  ft.  X  1  in. 

For  each  Double  Lock  (PI.  30,  Fig.  1)  4  legs  22  to  25  ft.  x  7  in. 
tip;  2  straining  beams  25  ft.  x  8  in.;  2  road  transoms  15  ft.  x  10  in.; 

2  frame  transoms  15  ft.  x  6  in.;  2  ledgers  15  ft.  x  5  to  6  in.;  4 
braces  20  ft.  x  3  in.;  2  shore  sills  15  ft.  x  6  in.  Lashings,  8  transom 
50  ft.  X  5^  in.;  14  ledger  and  brace  30  ft.  x  %  in.;  10  balk  20  ft.  x 
1-3  in.;  4  foot  50  ft.  x  1  in.;  8  guy  150  ft.  x  1  in.;  besides  axes  and 
other  tools,  and  anchorages,  holdfasts,  etc.,  on  banks. 

For  each  Single  Sling  (Fig.  2)  4  legs  35  to  45  ft.  x  6  in.  tip; 

3  top  and  fork  transoms  15  ft.  x  6  in.;  3  road  transoms  15  ft.  x  10 
in.;  2  ledgers  15  ft.  x  4  to  6  in.;  4  braces  20  ft.  x  3  in.;  2  shore  sills 
15  ft.  X  6  in.;  10  balks  30  ft.  x  6  in.;  4  side  rails  30  ft.  x  4  to  6  in. 
Lashings  of  same  number,  size  and  length  as  for  Double  Lock. 
Stiffening  will  require  additional  spars  and  lashings,  depending 
upon  the  method  used. 

For  each  'I?reble  Sling  (Fig.  3)  4  legs  50  ft.  x  6  in.  tip;  5  road 
transoms  15  ft.  x  10  in.;  3  top  and  fork  transoms  15  ft.  x  G  in.;  2 


Spar  Bridges.  139 

lower  ledgers  15  ft.  x  4  to  6  in.;  4  lower  braces  20  ft.  x  3  in.;  4  upper 
braces  18  ft.  x  3  in.;  2  shore  sills  15  ft.  x  6  in.;  15  balks  5  ft.  longer 
than  1-3  span  x  6  in.;  6  side  rails  5  ft.  longer  than  1-3  span  x  4  to 
G  in.;  6  sling  racking  sticks  10  ft.  x  4  in.  Lashings,  4  foot  50  ft. 
X  1  in.;  8  guy  150  ft.  x  1  in.;  24  ledger  and  brace  30  ft.  x  ^^  in.; 
8  transom  50  ft.  x  %  in.;  40  or  50  balk  20  ft,  x  1-3  in.  Stiffening 
will  require  additional  spars  and  lashings,  depending  upon  the 
method  used. 

For  Suspension  Bridge  200  ft.  long  (PL  40a,  Fig.  1)  4  to  8  ca- 
bles 180  ft.  X  1  in.;  16  cable  seizings  of  yarn  18  ft.  long;  12  lash- 
ings 50  ft.  X  2-3  in.;  10  lashings  30  ft.  x  ^^  in.;  100  lashings  20  ft. 
X  1-3  in.;  2  steel  wire  cables  400  ft.  x  1  2-3  in.;  4  standards  26  ft.  x 
10  in.  tip;  4  braces  22  ft.  x  3^^  in.  tip;  2  caps  12  ft.  x  10  in.;  2  sills 

15  ft.  X  10  in.;  4  back  struts  36  ft.  x  4  in.  tip;  4  side  struts  32  ft.  x 
3  in.  tip;  4  cable  props  30  ft.  x  5  in.  tip;  4  horizontal  ties  30  ft.  x 
3  in.  tip;  21  transoms  10  ft.  x  6  in.;  80  balks  13  ft.  x  6  in.;  40  side 
rails  20  ft.  x  6  in.;  for  anchorages  16  spars  5  ft.  x  7  in.  tip;  2  spars 

16  ft.  X  20  in.;  2  spars  16  ft.  x  12  in.  %  round;  10  spars  16  ft.  x  8 
in.  %  round;  4  back  ties  50  ft.  x  2-3  in.  steel  rope;  4  ties  35  ft.  x  ^ 
in.  steel  rope;  40  slings  total  600  ft.  x  %  in.  steel  rope;  4  guys  50 
ft.  x  1  in.;  4  rope  ladders. 

For  Suspension  Bridge  100  ft.  long  (Fig.  5)  4  to  8  cables,  12 
cable  seizings,  4  lashings,  12  lashings,  30  lashings  as  above;  2 
cables  180  ft.  x  3  in.  hemp  or  2  in.  steel;  2  anchor  spars  18  ft.  x  15 
in.;  10  transoms  12  ft.  x  4  in.;  4  balks  25  ft.  x  6  in.;  10  side  rails  20 
ft.  X  4  in. ;  materials  for  piers  depending  on  circumstances. 

For  Suspension  Bridge  130  ft.  long  (Fig.  6)  4  to  8  cables,  12 
cable  seizings,  9  lashings,  104  lashings,  280  lashings  as  above;  4 
cables  200  ft.  x  2  2-3  in.  hemp  or  IV2  in.  steel;  2  anchor  spars  18  ft.  x 
18  in.;  44  trestle  legs  13  ft.  x  3  in.  tip;  44  braces  15  ft.  x  2  in.  tip;  22 
transoms  9  ft.  x  4  in.;  80  ledgers  12  ft.  x  2  in.;  20  cable  ledgers  12 
ft.  X  5  in.;  2  shore  sills  10  ft.  x  5  in.;  48  balks  14  ft.  x  5  in.;  28  side 
rails  20  ft.  x  5  in.;  materials  for  piers  depending  on  circumstances. 

Besides  the  above  materials,  there  will  be  required  tools  for 
cutting  timber,  tackles  for  raising  frames,  shovels,  pickets,  etc., 
and,  where  not  mentioned,  the  ordinary  amounts  of  balks,  chess, 
side  rails,  etc. 


CHAl»TEJt  XVl.-  tloating  Bridged. 

288.— The  passage  of  a  stream  may  be  effected,  in  many  cases, 
as  described  in  the  preceding  chapter.  If  the  methods  there  laid 
down  are  not  suitable  or  expedient,  and  the  stream  cannot  be 
forded,  then  resort  must  be  had  to  ferrying  by  boats,  rafts,  flying 
bridges,  or  to  floating  bridges. 

289.— The  selection  of  a  place  and  means  of  crossing  a  river 
is  determined  by  a  reconnaissance,  which  should  be  as  detailed 
and  extensive  as  circumstances  will  permit,  and  embrace  the 
following:—  / 

(a)  The  nature  of  the  banks. 

(h)  The  nature  of  the  bed. 

(c)  Position  and  depth  of  fords. 

(d)  Strength  of  the  current. 

(e)  Whether  tidal  or  otherwise. 

(f)  Probability  and  extent  of  floods. 

290.— Fords.  A  stream  with  a  moderate  current  may  be 
forded  by  infantry  when  its  depth  does  not  exceed  3  ft.,  and  by 
cavalry  and  carriages  when  its  depth  is  about  4  ft.  The  requi- 
sites of  a  good  ford  are:— 

(a)  Banks  low,  but  not  marshy. 

(h)  Water  attaining  its  depth  gradually. 

(c)  Current  moderate. 

(d)  Stream  not  subject  to  freshets. 

(e)  Bottom  even,  hard,  and  tenacious. 

291.— In  a  mountainous  country,  the  bed  of  a  stream  is  likely 
to  be  covered  with  large  stones,  rendering  the  passage  of  car- 
riages impracticable.  In  level  countries,  the  bed  of  the  stream 
may  be  composed  of  mud  or  quicksand,  rendering  passage  by 
fording  impossible.  In  some  cases,  the  bottom  is  composed  of 
fine  sand,  which  is  hard  enough,  but  which,  by  the  action  of  the 
hoofs  of  the  animals,  is  stirred  up;  the  current  then  carries  the 
sand  away  and  the  ford  is  deepened,  perhaps  so  much  as  to  be- 
come unfordable.    The  best  bottom  is  coarse  gravel. 

292.— Fords  are  usually  found  In  the  wider  and  more  rapid 
parts  of  a  stream.  A  straight  reach  gives  the  most  uniform 
depth.  At  bends,  the  depth  will  generally  be  greater  at  the  con- 
cave bank  and  less  at  the  convex.    (PI.  41,  Figs.  1  and  3.) 


PLATE  41. 


-i^ ^ 


1^2  Floating  Bridges. 

293.— To  determine  the  position  of  a  ford:— 

(1)  A  number  of  mounted  men  may  be  sent  across  wherever 
there  is  a  probability  of  the  river  being  shallow  enough. 

•  (2)  Most  certain  method.  Float  down  the  stream  in  a  boat, 
keeping  in  the  swiftest  part  of  the  current,  where  the  water  is 
usually  deepest.  Hang  a  sounding  line  of  the  proper  length  over 
the  stern.    When  this  touches  bottom,  sound  across  the  stream. 

When  a  ford  is  discovered,  it  should  be  marked  by  stakes;  re- 
markable objects  on  the  shore  should  be  noted;  and  a  stake 
planted  at  the  water's  edge  and  marked,  in  order  that  any  rise 
in  the  water  may  be  at  once  evident. 

294.— A  stream,  otherwise  unfordable,  may  be  passed:— 

(1)  By  crossing  it  in  a  slanting  direction.    (Fig.  2.) 

(2)  When  the  unfordable  portion  is  not  over  8  or  10  yards,  this 
may  be  filled  in  with  fascines  loaded  with  stones.    (Fig.  4.) 

(3)  When  the  bottom  is  muddy,  it  may  be  covered  with  bun- 
dles of  coarse  grass,  rushes,  or  twigs,  sunk  by  means  of  stones. 

(4)  A  portion  of  the  water  may  be  diverted  from  its  natural 
channel.    (Fig.  5.) 

295.— In  passing  a  stream  by  fording,  if  it  is  deep  and  the  cur- 
rent at  all  swift,  the  following  precautions  should  be  taken:— 

(a)  Troops  passing  in  column  should  do  so  at  a  considerable 
interval,  in  order  to  avoid  choking  the  stream. 

(h)  If  boats  are  to  be  had,  a  few  should  be  stationed  below  the 
ford,  to  assist  men  who  may  be  carried  down  by  the  current. 

(c)  If  boats  cannot  be  procured,  mounted  men  may  perform 
the  duties  described  in  the  foregoing  provision. 

(d)  In  place  of  provisions  "b'*  and  "c,"  a  life  line,  held  up  by 
casks,  may  be  stretched  across  the  stream. 

(e)  In  order  to  break  the  force  of  the  current,  cavalry  may  be 
stationed  in  the  stream,  above  the  point  of  crossing. 

296.— After  a  freshet,  a  ford  should  always  be  reexamined, 
lest  some  alteration  may  have  taken  place  in  the  bed  of  the 
stream.  The  banks  of  a  stream  to  be  forded  should,  if  necessary, 
be  cut  down. 

The  velocity  of  a  stream  may  be  determined  by  throwing  in  a 
light  rod,  so  weighted  as  to  stand  vertically.  Note  the  distance 
passed  over  in  a  certain  number. of  seconds;  then,  7-10  the  mean 
number  of  feet  per  second  gives  the  velocity  in  miles  per  hour. 


Floating  Bridges.  143 

297.— Ice.  In  high  latitudes,  duiiug  the  winter,  rivers  are  fre- 
quently covered  with  ice  of  sufficient  thickness  to  sustain  the 
heaviest  loads.  This  means  of  passing  a  stream  should  be  used 
with  great  circumspection.  A  change  of  temperature  may  not 
only  suddenly  destroy  the  natural  bridge,  but  render  the  river 
impassable  by  any  method,  for  a  considerable  time,  in  conse- 
quence of  floating  ice. 

298.— Ice,  in  order  to  allow  of  passage,  should  be  of  the  follow- 
ing thickness:— 
For  Infantry,  single  file,  2  yds.  distance,  on  a  line  of 

planks  2  in. 

For  Cavalry  or  light  guns,  with  intervals 4  in. 

Heavy  field-pieces 5  to  7  in. 

Heaviest  loads 10  in. 

299.— When  there  is  any  doubt  as  to  the  strength  of  the  ice, 
two  tracks  of  plank  may  be  laid  for  the  carriage  wheels  to  run 
on,  or  the  wagon  may  be  transformed  into  a  kind  of  sled  by  fas- 
tening two  planks  under  the  wheels.    (Fig.  6.) 

The  thickness  of  ice  may  be  increased,  when  the  temperature 
is  low,  by  throwing  water  on  it.  When  a  stream  is  frozen  on  each 
side  but  open  in  the  middle,  in  consequence  of  the  velocity  of  the 
current,  a  boom  stretched  across  the  open  space  will  often  check 
the  velocity  sufiiciently  to  allow  the  water  to  freeze. 

300.— If  a  stream  cannot  be  forded,  it  may  be  crossed  by  fer- 
rying or  by  constructing  a  bridge.  Ferrying  may  be  by  boat, 
raft,  or  flying  bridge;  rowed,  sheered,  or  hauled  across. 

301.— Ferrying  by  Boat.  All  boats  available  should  be 
collected  and  taken  to  the  chosen  point  of  passage.  The  banks  of 
the  stream,  if  steep,  should  bo  cut  down  to  facilitate  embarkation. 
The  landing  should  be  farther  down  the  stream  than  the  point 
of  starting.  The  boats  should  be  arranged  along  the  shore  and 
numbered.  Entrance  to  the  boats  should  be  by  file,  the  soldiers 
taking  positions  on  opposite  sides  alternately.  Where  the  water 
is  shallow  near  the  shore,  the  boat  should  not  approach  the  bank 
so  closely  as  to  ground  as  the  men  file  in.  The  unloading  should 
be  made  in  the  same  manner  as  the  embarkation — i.  e.,  by  file 
alternately  from  each  side  of  the  boat.  During  the  transit,  the 
men  should  remain  in  position  and  not  rise  up  suddenly  when  the 
boat  lurches. 

In  passing  artillery,  the  piece  should  be  dismounted.    Horses 


144  Floating  Bridges. 

should,  ordinarily,  be  made  to  swim.  However,  if  the  boats  are 
large  enough,  the  bottoms  may  be  covered  with  plank,  and  the 
horses  placed  crosswise,  facing  alternately  up  and  down  stream. 

302.— Ferrying  by  Raft.  Rafts  may  be  made  of  logs,  lum- 
ber, casks,  and  other  material  suitable  for  the  purpose.  Their 
construction  is  the  same  as  explained  for  piers  of  bridges,  hence 
only  two  expedients  will  be  mentioned  here. 

303.— The  Canvas  Raft.  No  other  material  being  available, 
small  rafts  can  be  constructed  by  the  use  of  canvas  about  8  x 
12  ft,  and  brushwood.  Wet  the  canvas  to  make  it  water-proof, 
and  lay  it  out  on  the  ground.  Across  the  width  place  sticks  in 
layers,  the  longest  near  the  middle.  The  sides  should  be  strength- 
ened by  heavy  sticks  placed  lengthwise.  The  pile  of  sticks 
should  be  about  4  ft.  wide  in  the  center  and  sloping  off  slightly 
towards  the  ends,  3  ft.  high  and  8  ft.  long.  Over  this  pile  a  sec- 
ond piece  of  canvas,  after  being  wet,  should  be  placed.  The 
sides  of  the  canvas  on  the  ground  are  now  drawn  over  toward 
each  other  and  lashed  securely  with  a  lariat.  The  ends  are  folded 
neatly,  brought  up  towards  each  other,  and  lashed.  If  care  is 
taken  to  w^et  the  canvas  thoroughly  and  make  it  water-tight,  this 
raft  will  carry  three  troopers  with  their  arms  and  accouterments. 
By  lashing  several  together,  a  larger  number  of  men,  with  their 
arms  and  accouterments,  can  be  carried. 

304.— Rafts  of  Skins.  Bags,  made  of  the  skins  of  animals, 
Inflated  with  air  or  stuffed  with  hay  or  straw,  can  be  utilized  for 
crossing  streams,  and  have  been  used  from  ancient  times. 

305.— Rafts  are  more  suitable  for  the  embarkation  and  landing 
of  troops  of  all  arms  than  boats.  They  will  carry  a  larger  num- 
ber each  trip,  are  not  so  easily  injured  by  the  fire  of  the  enemy, 
and  draw  little  water.  On  the  other  hand,  they  cannot  be  navi- 
gated with  the  same  facility  as  boats,  move  much  more  slowly, 
and  hence  keep  the  troops  much  longer  under  fire;  cannot  be 
directed  with  certainty  on  a  fixed  point  when  the  stream  is  rapid, 
and,  If  the  passage  is  to  be  effected  secretly,  the  time  required  for 
their  construction  Is  too  long  to  admit  of  their  use. 

306.— The  Floating  Bridge.*     This  may  be  formed   of  two 

_*A  simple  modification  of  the  floating  bridge  is  an  expedient  used  in  the  Philip- 
pine Islands  for  floating  wagons  across  deep  streams. 

This  is  merely  to  run  the  vehicle  into  the  stream  astride  of  two  bancas  (narrow 
dugouts),  the  axles  resting  on  the  gunwales  and  the  boats  as  far  apart  as  the 
hubs  of  the  wheels  will  allow.  Wagons  can  thus  be  readily  crossed  without  un- 
loading, provided  the  bancas  are  large  enough  to  support  the  weight. 


Floating  Bridges.  145 

boats  covered  with  a  platform,  constructed  as  follows:— (PI.  42, 
Fig.  1. — The  lashings  and  side  rails  are  omitted.)  From  5  to  7 
beams  of  the  same  thicliness  are  laid  across  the  two  boats,  the 
intervals  between  the  beams  being  equal,  and  such  that  the  cover- 
ing planks  extend  1  ft.  beyond  the  extreme  beams.  The  interval 
between  the  boats  is  such  as  to  allow  the  beams  to  extend  2  ft. 
beyond  the  gunwales.  The  beams  are  lashed  to  the  boats,  the 
covering  planks  are  kept  in  place  by  2  side  rails,  laid  directly  over 
the  outer  beams,  and  lashed  down  to  them;  the  extreme  planks 
should  be  nailed  down. 

The  floating  bridge  can  be  navigated  by  oars  with  nearly  the 
same  facility  as  a  boat. 

307.— The  Rope  Ferry.  The  rope  ferry,  which  is  used  in  slug- 
gish streams,  consists  of  a  floating  support,  either  a  raft,  float- 
ing bridge,  or  a  large  boat.  It  is  drawn  by  hand  along  a  rope 
stretched  from  shore  to  shore. 

308.— The  Trail  Bridge.  This  is  employed  in  streams  not 
more  than  150  yds.  in  width,  and  whose  current  is  not  less  than  3 
ft.  per  second,  or  2  1-10  miles  per  hour.  The  rope  must  be  main- 
tained above  the  surface  of  the  water,  and,  consequently,  must  be 
drawn  very  tightly  by  means  of  a  windlass,  blocks,  and  falls,  or 
similar  expedients;  it  must,  also,  at  each  bank,  be  raised  some  dis- 
tance above  the  water.*     (PI.  42,  Fig.  3.) 


*A  convenient  expedient  for  tightening  the  rope  when  no  blocks  are  at  hand  is 
here  shown. 


Another  rope  "r"  is  attached  to  the  ferry  rope  *'R"  at  "a"  by  a  stopper  hitch  and 
then  passed  round  the  holdfast  and  through  a  loop  "b"  in  the  ferry  rope:  power  is 
then  applied  as  indicated  by  the  arrow,  the  slack  of  the  ferry  rope  being  taken  in 
at  "c."  When  the  ferry  rope  is  taut,  enough  the  attached  rope  "r"  is  eased  off 
thus  letting  the  strain  come  gradually  upon  the  cable  again. 


PLATE  42. 


Fig.l. 


Fig.  2. 


J  PLATE  43. 


148  Floating  Bridges. 

The  raft,  or  boat,  is  attached  to  a  pulley,  which  runs  on  a  sheer 
line,  and  by  means  of  a  rudder  is  given  such  a  position  that  its 
side  makes  an  angle  of  about  55°  with  the  direction  of  the  cur- 
rent. The  angle  of  55°  with  the  current  divides  its  force  against 
the  side  of  the  boat  into  two  components:  one,  perpendicular  to 
the  sheer  line,  which  is  counteracted  by  the  resistance  of  this 
line;  the  other,  parallel  to  it,  which  moves  the  boat.  A  boat  for 
this  kind  of  ferry  should  be  narrow  and  deep,  with  nearly  ver- 
tical sides. 

If  a  raft  is  used,  it  should  be  lozenge-shaped,  the  acute  angle 
being  about  55°.  When  two  sides  are  parallel  to  the  current,  the 
up-stream  side  will  then  be  in  the  most  favorable  position  for 
passage.    (PI.  43,  Fig.  8.) 

309.— The  Flying  Bridge.  The  character  of  the  float  for 
this  ferry  is  the  same  as  in  the  preceding  case.  (PI.  41,  Fig.  7; 
PI.  42,  Fig.  2.)  This  bridge  is  resorted  to  when  the  stream  is 
wider  than  150  yds.  The  strain  on  the  sheer  line  being  very 
great,  it  is  replaced  by  a  cable  anchored  in  mid-stream,  in  which 
case  the  float  would  swing  between  two  landing  piers;  or  by  two 
cables,  one  anchored  on  either  bank,  the  float  swinging  between 
four  piers.  The  latter  requires  less  skill  in  manipulation.  The 
angle  w^hich  the  float  makes  with  the  current  is  the  same  as  that 
of  the  **trail"  bridge.  A  sharp  bend  may  be  utilized  for  anchor- 
ing the  cable,  as  shown  in  PI.  42,  Fig.  4. 

The  length  of  a  swinging  cable  should  be  1%  to  2  times  the 
width  of  the  stream.  The  cable  should  be  supported  on  inter- 
mediate buoys  or  floats,  to  prevent  it  dragging  in  the  water. 

310.— Floating  Bridges  are  composed  of  a  roadway  and  its 
supports.  The  roadway  is  explained  in  the  preceding  chapter. 
The  supports  are  floating,  as  pontons,  boats  of  commerce,  rafts 
of  barrels,  logs,  lumber,  inflated  skins  of  animals,  or  other  mate- 
rial. The  supports  are  called  floating  piers.  It  is  from  the  char- 
acter of  the  support  that  the  bridge  derives  its  name. 

311.— In  constructing  a  floating  bridge,  the  site  should  be  first 
selected  and  the  icidth  of  the  stream  measured. 

In  selecting  a  site,  the  following  points  should  be  noted:— 

(a)  Proximity  to  a  road.  As  the  approaches  to  floating 
bridges,  having  frequently  to  be  constructed  across  meadows,  give 


Floatmg  Bridges.  149 

*  mucli  trouble,  they  should  be  as  short  as  possible.  For  a  similar 
reason,  marshy  banks  are  undesirable. 

(h)  The  bed  of  the  stream,  if  anchors  are  required,  should 
afford  good  holding  ground. 

(cj  A  bridge  can  be  best  defended  if  constructed  at  a  reenter- 
ing bend  of  a  river. 

(dj  Use  can  frequently  be  made  of  islands  to  economize 
material. 

312. — In  measuring  the  loidth  of  the  stream,  if  it  cannot  be 
done  directly,  some  one  of  the  methods  explained  in  Chap.  III. 
can  be  used. 

313.— It  should  be  remembered  that  a  wide  roadway  gives 
greater  steadiness  than  a  narrow  one.  In  making  calculations 
for  buoyancy,  the  weight  of  a  9  ft.  roadway  may  be  taken  at  80 
lbs.  per  running  foot. 

314.— Piers.  Of  whatever  material  the  floating  pier  is  made, 
the  following  points  should  be  observed:— 

(1)  The  available  buoyancy  of  each  pier  should  be  sufficient  to 
support  the  heaviest  load  that  can  be  brought  on  one  bay  of  the 
bridge. 

(2)  Piers  should  be  connected  with  each  other,  at  their  extremi- 
ties, by  tie  balks  or  lashings. 

(3)  To  insure  steadiness,  the  length  of  a  pier  should  be  at  least 
twice  the  width  of  the  roadway. 

(4)  The  water  way  between  piers  should,  if  possible,  be  more 
than  the  width  of  two  piers,  never  less. 

315. — Piers  of  open  boats.  In  forming  a  pier  of  open  boats, 
the  following  precautions  should  be  taken:— 

(1)  The  boat  should  not  be  immersed  deeper  than  within  1  ft. 
of  the  gunwale. 

1 2)  If  the  water  is  rough,  or  the  current  extremely  swift,  -a 
boat  should  not  be  immersed  deeper  than  within  1  ft.  4  in.  of  the 
gunwale. 

(3)  Boats  should  be  placed  in  bridge  with  bows  up  stream  or 
toward  the  current. 

(4)  If  the  stream  is  tidal,  the  bows  of  the  boats  should  be  alter- 
nately up  and  down  stream. 

(5)  Unless  the  boat  is  very  heavy  and  strong,  the  balks  should 


150  Floating  Bridges. 

not  rest  on  the  gunwales;  a  central  transom  should  be  impro- 
vised by  resting  a  timber  on  the  thwarts,  or  seats,  blocking  up 
from  underneath  and  bringing  the  weight  directly  on  the  keel- 
son.   (PI.  43,  Figs.  6  and  7.) 

(0)  T/arge  boats  should  be  placed  where  the  current  is  swiftest, 
also  as  the  first  and  last  boats  in  bridge. 

316.— The  buoyancy  of  a  boat  may  be  found  by  one  of  the 
following  rules:— 

(1)  To  find  the  available  buoyancy  load  the  boat  with  unarmed 
men  to  a  safe  depth.  Multiply  the  number  of  men  thus  loaded  by 
160.    The  result  will  be  the  available  buoyancy  in  pounds, 

(2)  If  the  boat  is  afloat  and  empty,  the  available  buoyancy  may 
be  found  by  calculating  the  volume  between  the  then  water  line 
and  the  "safe  load"  line,  and  multiplying  by  62%. 

(3)  To  find  the  total  buoyancy.  If  the  boat  is  of  nearly  uni- 
form section,  the  area  of  the  section  multiplied  by  the  length  of 
the  boat  will  give  the  cubic  contents.  A  cubic  foot  of  water 
weighs  621^2  pounds. 

Hence,  If  the  dimensions  of  a  boat  are  taken  in  feet,  the  con- 
tents will  be  cubic  feet,  and  this,  multiplied  by  62%,  will  give  the 
displacement  of  the  boat:  from  this  subtract  the  weight  of  the 
boat:  this  will  give  the  total  buoyancy. 

317.— To  find  the  length  of  a  bay.  First  find  the  avail- 
able buoyancy  of  the  boat.  Then  find  the  weight  per  running 
foot  of  the  load  the  bridge  is  to  bear,  and  to  this  add  the  weight 
per  running  foot  of  the  roadway.  Divide  the  available  buoyancy 
by  this  sum.  The  quotient  will  be  the  distance  in  feet  from  center 
lo  CRnter  that  boats  should  be  placed  apart.  Thus: — Suppose  th'- 
weight  per  running  foot  is  480  lbs.,  that  the  roadway  is  80  lbs. 
per  running  foot.  .*.  480+80=560.  The  available  buoyancy  is 
found  by  one  of  the  preceding  rules  to  be  5,600  lbs.  .*.  5,600  -^ 
560=10,  the  distance  in  feet  between  centers  of  boats. 

318.— The  open  boats  may  be:— (1)  Those  of  commerce  usually 
found  on  streams.  (2)  Regularly  constructed  pontons.  (3)  Im- 
provised boats. 

The  first  class  requires  no  description.  The  second  class  com- 
prises the  canvas  ponton  used  In  the  Advance  Guard  Train,  and 
the  boat  or  barge  used  in  the  Reserve  Train,  of  the  U.  S. 


Floating  Bridges. 


151 


319.— The  table  below  gives  the  dimensions  of  the  ponton  In 
the  U.  S.  Advance  Guard  Train,  shown  in  PI.  47. 
Canvas  Ponton  21'  x  5'  4"  x  2'  4".    Weight,  510  lbs. 
Balks  22'  x  4y2"  x  4y2". 
Side  Rails  same  as  BalliS. 
Chess  11'  X  12"  X  1%". 

WEIGHTS  FOR  ADVANCK  GUARD  TRAIN. 


Wag"on. 


Total. 


lbs. 

1     lbs. 

lbs. 

1,750 

1,985 

3,735 

1,750 

1,856 

3,606 

1,750 

2,060 

3,810 

1,700 

1,938 

3,638 

1,217 

1,166 

2,385j 

Ponton 
Chess  .. 
Trestle 
Tool.  . . 
Forge.  . 

320.— The  table  below  gives  the  dimensions  of  the  ponton  in 
the  U.  S.  Reserve  Train,  shown  in  PI.  48. 

Ponton  31'  x  5'  8"  x  2'  7".    Weight,  1,600  lbs. 
Balks  27'  x  5"  x  5"  for  a  20'  span. 
Trestle  Balks  21'  8"  x  5"  x  5". 
Chess  13'  X  12"  x  IVa". 
Side  Rails  same  as  Balks. 

WEIGHTS  FOR  RESFRVE  TRAIN. 


Wagon. 

Ivoad. 

Total. 

Ponton 

lbs. 
2,200 
1,750 
2,200 
1,700 
2,217 

lbs. 
2,900 
2,280 
2,635 
2,100 
1,166 

lbs. 
5,100 

Chess 

4,030 

Trestle 

4,835 

Tool 

3,800 

Forge 

3,383 

321.— Improvised  Boats.  To  reduce  the  amount  of  transpor- 
tation required  by  an  army  is  a  very  important  consideration; 
hence  the  value  of  the  following  expedients. 

322.— The  Crib  Ponton.  This  boat  is  18  ft.  long,  5  ft.  wide, 
2%  ft.  deep  and  covered  with  canvas.  Construction.  (1)  Let 
stakes  4  ft.  long,  2^^  in.  in  diameter,  and  2  ft.  apart,  be  driven  into 
the  ground  (PI.  44,  Figs.  1,  2  and  8),  to  tlie  depth  of  about  1  ft.,  so 
as  to  enclose  a  space  of  the  proper  si^e  for  the  top  of  the  boat 


PLATE  44. 


Fig  1. 


Illllll 


Pig.  2 


^4fh^U9/d^'>^'hA'^J^^ 


Fig.  3. 
I     I     I     I 


Fig.4. 


Fig.  6. 


Fig.7 


!^^4 


Fig.a 


Fig.  5. 


iniuinii  iiiiiiniiuiiiuiiiiiHnnnm  iMi 


■aWRHIHH^WPWWW 


Floating  Bridges.  153 

The  tops  of  the  stakes  should  be  In  the  same  horizontal  plane. 
This  may  be  tested  by  placing  a  sti*aight-edge  on  them.  Those 
that  are  too  high  can  then  be  driven  down. 

(2)  Nail  boards  against  the  outside  of  the  stakes,  extending 
4  in.  over  their  tops. 

(3)  Cross-pieces,  of  the  same  diameter  as  the  stakes,  are  laid 
across  the  tops  and  pinned  down  upon  them  with  wooden  pins. 

(4)  Nail  the  side  boards  to  the  ends  of  the  cross-pieces,  and 
cover  the  bottom  of  the  boat,  which  in  its  inverted  position  is 
now  on  top,  with  boards,  and  nail  the  projecting  edges  of  the 
side  boards  to  the  bottom  securely. 

(5)  Finish  boarding  sides  and  ends  to  the  proper  depth. 

(6)  The  frame  is  now  ready  to  be  covered  with  canvas.  For  a 
boat  of  the  foregoing  dimensions,  the  canvas  should  be  23%  ft.  x 
10%  ft.,  about  6  in.  being  allowed  for  lap.  The  canvas  may  be  put 
together  in  any  number  of  pieces  by  daubing  the  edges  of  the 
seams  with  a  water-proof  composition  and  connecting  them  with 
ordinary  carpet  tacks. 

(7)  The  canvas  having  been  prepared,  it  should  now  be  coated 
with  a  water-proof  composition.  Tallow,  put  on  hot,  will  do  if 
nothing  better  can  be  found. 

(8)  Place  the  canvas  on  the  frame,  coated  side  downward.  Tack 
the  canvas  to  the  frame  and  cover  with  water-proof  composition. 

(9)  Spike  or  pin  2  or  3  stout  poles  to  the  bottom  longitudinally 
(not  shown  in  drawing)  to  keep  the  bottom  from  abrading.  If 
these  poles  are  allowed  to  project  about  6  in.  at  each  end,  they 
will  assist  in  launching. 

(10)  Loosen  the  stakes  from  the  ground  by  means  of  levers. 
Turn  the  boat  over  and  saw  off  the  stakes  about  2  in.  below  the 
top  edge  of  the  side  and  end  boards. 

(11)  Pin  stout  poles  to  the  top  of  the  stakes  on  the  sides  and 
ends,  and  nail  the  side  and  end  boards  securely  to  them. 

(12)  The  side  poles  should  project  about  6  in.  beyond  the  ends 
corresponding  to  those  on  the  bottom,  and  be  lashed  to  the  bot- 
tom poles  by  means  of  a  rope  loop  and  rack  stick.  (Not  shown  in 
drawing.) 

(13)  Turn  the  canvas  over  the  top  poles  and  tack  ft  down.  The 
boat  Is  finished. 

323. — Th^  Box  Ponton.   In  localities  where  planks  and  hoards 


154  Floating  Bridges. 

can  be  conveniently  procured,  pontons  may  be  constructed  very 
expeditiously  by  placing  two  partitions  of  2  in  plank,  each  5  ft. 
long  and  2%  ft.  high,  in  parallel  positions,  on  the  top  and  ends  of 
which  boards  are  nailed.  (PI.  44,  Fig.  4.)  The  box  thus  formed 
to  be  covered  with  pitched  canvas,  as  described  in  the  mode  of 
constructing  crib  pontons.  Where  sound  lumber  is  at  hand,  the 
box  ponton  will  be  more  easily  and  expeditiously  constructed 
than  the  crib  ponton,  but  if  plank  is  not  at  hand  it  may  be  prefer- 
able to  use  poles  or  split  timber  rather  than  wait  for  it. 

324.— Wagon  Body  Ponton.  Ordinary  wagon  bodies,  cov- 
ered with  water-proof  canvas  or  India  rubber  blankets,  may  be 
used  either  as  boats  or  pontons.  The  small  capacity  of  the 
wagon  body  requires  such  pontons  to  be  placed  more  closely,  to 
compensate  for  it. 

325. — ^Piers  of  Barrels.  In  order  to  determine  the  number  of 
barrels  necessary  to  form  a  pier,  the  buoyancy  of  a  barrel  must  be 
calculated.    This  maybe  done  by  one  of  the  following  rules:— 

(1)  Find  the  contents  of  the  barrel  in  gallons  and  multiply  this 
by  8  1-3;  the  result  will  be  almost  the  total  buoyancy  in  pounds. 

(2)  By  the  formula 

5c2  1  —  W  =  X 
in  which  c  is  the  circumference  of  the  barrel  in  feet  half  way  be- 
tween the  bung  and  the  extreme  end;  1  is  the  length  in  feet,  ex- 
clusive of  projections,  measured  along  a  stave,  and  W  is  the 
weight  of  the  barrel  in  pounds;  x  being  the  total  buoyancy. 
If  the  barrel  is  closed,  9-10  of  the  total  buoyancy  equals  the  avail- 
ahle  buoyancy. 

326. — To  find  the  distance  between  two  piers  of  barrels:  Find 
the  available  buoyancy  of  each  barrel.  Multiply  this  by  the  num- 
ber of  barrels  in  the  pier.  This  gives  the  available  buoyancy  of  the 
pier.  To  the  weight  per  running  foot  that  the  bridge  is  to  bear 
add  the  weight  per  running  foot  of  the  superstructure.  Divide 
the  available  buoyancy  of  the  pier  by  this  sum;  the  quotient  will 
be  the  required  distance  in  feet  between  centers  of  piers. 

327. — In  regard  to  piers  of  barrels,  the  following  should  be 
noted: 

(1)  That  piers  of  barrels,  when  in  bridge,  should  always  be  rig- 
idly connected  to  each  other  at  their  ends  by  tie  balks. 


Floating  Bridges.  155 

(2)  That  the  tie  balks  should  be  lashed  to  both  gunnels  of  each 
pier. 

(3)  That  while  the  roadway  balks  may  not  be  lashed  to  the 
gunnels  and  to  each  other,  it  should  be  done  if  there  is  much 
sway  to  the  bridge. 

328. — Piers  of  Open  Barrels.  This  is  the  simplest  and  most 
convenient  method  of  using  barrels  for  piers,  as  it  requires  only 
a  few  nails  and  poles,  dispensing  with  ropes,  which  are  sometimes 
hard  to  procure. 

To  make  a  raft  of  this  kind,  as  shown  in  PI.  44,  Figs.  5  and  6, 
stand  10  or  12  barrels  side  by  side,  touching  each  other;  nail  4 
poles  across  the*  outside  of  the  barrels,  two  at  top,  two  at  bottom, 
the  nails  being  driven  from  the  inside  into  the  poles,  which,  as 
the  heads  are  out,  can  easily  be  done.  Place  another  row  of  bar- 
rels beside  the  row  thus  fastened  together  and  nail  them  to  the 
two  poles  of  this  row.  Nail  two  poles  to  the  outside  of  the  second 
row  of  barrels,  one  at  top  and  one  at  bottom;  push  the  barrels 
thus  connected  into  the  water. 

If  too  many  rows  are  connected  on  land  they  will  become  too 
heavy  to  handle.  Any  number  of  rows,  however,  can  be  attached 
in  the  manner  described  above.  When  the  raft  is  completed,  the 
projecting  ends  of  the  poles  outside  are  lashed  together,  and,  at 
the  points  of  contact  of  the  barrels,  a  stout  wire  nail  should  be 
driven  through  and  clinched. 

329. — The  total  buoyancy  of  a  barrel  may  be  calculated  by  the 
formula  given  above.  If  this  should  be  400  lbs.,  the  safe  load  for 
smooth  water  would  be  at  least  300  lbs.;  that  is,  the  available 
buoyancy  is  about  %  the  total  buoyancy.  A  square  raft  of  10 
such  barrels  to  a  side  would  carry  safely  30,000  lbs. 

330.— Piers  of  Closed  Barrels.  The  usual  method  of  forming 
large  barrels  into  a  pier  is  shown  in  PI.  43,  Figs.  1  and  2.  The  fol- 
lowing are  the  successive  steps  in  its  construction:— 

Stores  required  for  a  pier  of  7  barrels:  7  barrels;  2  gunnels;  "2 
slings;  12  braces. 

To  build  a  pier  of  the  foregoing  stores,  1  N.  C.  O.  and  16  men 
will  be  required.  The  detachment  is  marched  to  the  site  on 
which  the  material  is  placed  and  forms  the  barrels  into  piers  by  the 
following  commands  and  means,  4  men  being  detailed  as  gunnel- 
men  and  12  as  bracemen. 


156  Floating  Bridges. 

(1)  Align  barrels.  At  this  command,  the  barrels  are  brought  to 
the  designated  place  by  the  bracemen  and  aligned,  touching  each 
other,  bung  uppermost. 

(2)  Place  gunnels.  At  this  command,  the  gunnels  are  placed 
on  the  outer  ends  of  the  barrels  by  the  gunnelmen. 

(3)  Adjust  slings.  At  this  command,  gunnelmen  bring  up 
the  slings  and  stand  at  the  ends  of  the  gunnels,  the  bracemen  be- 
ing opposite  the  intervals  between  the  barrels.  The  gunnelmen  at 
one  end  place  the  eyes  of  the  slings  over  the  ends  of  the  gunnels, 
and  those  at  the  other  end  secure  the  slings  to  the  ends  of  the 
gunnels  by  a  round  turn  and  two  half-hitches.  The  bracemen 
keep  the  slings  under  the  ends  of  the  barrels  with  their  feet.  A 
sling  is  made  of  1  in.  rope  and  of  sufficient  length  for  an  eye  splice 
1  ft.  long,  at  one  end. 

(4)  Fasten  braces.  At  this  command,  the  bracemen,  having 
provided  themselves  with  braces,  pass  the  eye  of  the  brace  under 
the  sling  in  the  center  of  their  interval  the  end  passed  through 
the  eye  and  the  brace  hauled  taut,  the  sling  being  steadied  by 
either  foot.  The  brace  is  then  brought  up  outside  the  gunnel, 
directly  over  the  eye,  and  a  turn  round  the  gunnel  taken  to  the 
left  of  the  standing  part. 

(5)  Haul  taut.  At  this  command,  each  braceman  removes 
his  foot  from  the  sling  and  hauls  up  the  standing  part  of  his 
brace  with  his  right  hand,  holding  on  to  the  turn  with  his  left; 
as  soon  as  the  brace  is  taut,  the  turn  is  held  with  the  left  hand 
and  the  remainder  of  the  brace  in  a  coil  is  placed  on  the  barrel  to 
the  left. 

(6)  Cross  braces.  At  this  command,  each  braceman  takes  the 
brace  of  the  man  opposite  him  from  the  barrel  on  his  right,  pass- 
ing it  between  the  standing  part  of  his  brace  and  the  barrel  on 
his  left,  then  back  between  his  brace  and  the  barrel  on  his  right, 
keeping  the  turn  below  the  figure  of  eight  knot  on  his  own  brace. 
The  end  is  then  placed  on  the  barrel  on  his  right.  Each  man  then 
takes  back  his  own  brace  from  the  barrel  on  his  left,  passes  it  un- 
der the  gunnel  to  the  left  of  the  standing  part,  places  one  foot 
against  the  gunnel  and  hauls  taut. 

(7)  Rock  and  haul  taut.  The  bracemen,  assisted  by  the  gun- 
nelmen, at  this  command,  rock  the  pier  backwards  and  forwards, 
the  bracemen  taking  in  the  slack  of  their  braces.  ^ 


Floating  Bridges.  15'V 

(8)  Steady.  At  this  command,  the  bracemen  cease  rocking 
and  take  a  turn  round  the  gunnel  to  the  left  of  the  previous 
turns. 

(9)  Secure  braces.  At  this  command,  the  braces  are  made  fast 
by  two  half -hitches  round  the  two  parts  of  their  own  braces,  close 
lo  the  gunnels,  drawing  the  two  parts  close  together  and  placing 
the  spare  ends  of  the  braces  between  the  barrels. 

(10)  Turn  the  pier  to  the  right  and  adjust  sling.  At  this 
command,  the  bracemen  on  the  left  side,  assisted  by  the  gunnel- 
uien,  turn  the  pier  on  its  right  side.  The  bracemen  on  the  left 
feide  adjust  the  left  sling. 

(11)  Lower  the  pier,  turn  to  the  left,  and  adjust  sling. 
xVt  this  command,  the  bracemen  on  the  left,  assisted  by  the 
i»:unnelmen,  lower  the  pier.  The  bracemen  on  the  right,  assist- 
ed by  the  gunnelmen,  then  turn  the  pier  to  the  left.  The 
bracemen  on  the  right  then  adjust  the  right  sling.  The  pier  is 
complete. 

331. — Should  the  barrels  be  very  small,  they  may  be  put  to- 
gether as  above  described,  forming  small  piers.  These  can  then  be 
united  in  one  large  pier  by  cross  gunnels. 

332. — Another  method  of  forming  barrels  into  a  pier  is  as  fol- 
.ows:— (Figs.  3  and  4.) 

Fasten  the  braces  to  a  balk,  two  braces  for  each  barrel.  Stretch 
out  the  braces  perpendicular  to  the  balk  and  lay  the  barrels  bung 
uppermost,  end  to  end,  on  each  side  of  the  balk,  each  barrel  over 
its  own  braces.  Upon  the  cask  lay  two  gunnels,  fastened  together 
at  the  ends  and  one  or  two  intermediate  points  by  lashings,  the 
distance  between  the  gunnels  being  less  than  a  bung  diameter  of 
a  barrel.  Secure  the  braces  to  the  gunnels  by  two  round  turns  and 
two  half-hitches.  The  lashings  connecting  the  gunnels  are  then 
racked  up.  The  two  end  gunnel  lashings  are  lashed  to  the  balk 
beneath  the  barrels  and  these  lashings  are  racked  up  taut.  The 
pier  is  then  complete. 

333.— The  barrels  may  be  held  in  a  frames  as  shown  In  PI.  44, 
Mgs.  7  and  8. 

334.— Piers  of  Logs.  In  order  to  determine  the  number 
of  logs  necessary  to  form  a  pier,  the  buoyancy  of  a  log  must  be 
calculated. 


158  Floating  Bridges. 

To  find  the  total  buoyancy  of  a  log.  Multiply  the  solid  con- 
tents of  a  log  by  the  difference  between  the  weight  of  a  cubic  foot 
of  the  log  and  a  cubic  foot  of  water. 

335.— To  find  the  solid  contents  of  a  log. 

(1)  Take  a  mean  of  the  girths  or  circumference  at  the  ends  in 
feet  and  decimals.  Square  this  mean  and  multiply  it  by  the  dec- 
imal .07956.  Multiply  this  product  by  the  length  of  the  log  in 
feet. 

(2)  Multiply  twice  the  square  of  1-5  of  the  mean  girth  by  the 
length  of  the  trunk. 

336.— The  weight  per  cubic  foot  of  the  timbers  usually  met 
with  will  be  found  in  Chap.  XV. 

337.— Required  the  total  buoyancy  of  a  pine  log  whose  mean 
girth  is  6  ft.  and  whose  length  is  35  ft. 

Applying  rule  2,  we  have 

2X|X|X35  =  lOOi  cu.  ft. 

100  i  X  (62^  —  40)  =  100  f  X  221^  =  100.8  x  22.5  =  2,268  lbs. 

As  lumber  absorbs  water,  the  available  buoyancy  is  taken  as  5-6 
the  total  buoyancy. 

338.— To  form  a  pier  of  logs.  (PI.  43,  Fig.  5.)  The  larg- 
est and  longest  logs  should  be  selected.  Branches  and  knots 
should  be  trimmed  off.  The  ends  of  the  logs  should  be  painted  if 
the  raft  is  to  be  used  any  length  of  lime.  The  raft  should  be 
built  in  the  water.  Select  a  place  where  there  is  little  current 
and  where  the  bank  slopes  gently  to  the  stream.  Throw  the  tim- 
ber into  the  water  and  moor  it  close  to  the  shore.  Note  the  nat- 
ural position  of  each  log  in  the  water  before  putting  it  in  the  rart. 
The  up-stream  end  of  each  log  should  be  drawn  on  shore  and  bev- 
eled to  a  whistle  shape,  so  as  to  present  less  obstruction  to  the 
action  of  the  current. 

Arrange  the  timber  in  the  position  it  is  to  have  in  the  raft,  the 
butts  alternately  up  and  down  stream,  the  up-stream  ends  forming 
a  right  angle,  salient  up  stream.  The  first  log  is  brought  along- 
side the  shore  and  the  end  of  a  plank  or  a  small  trunk  of  a  tree 
fastened  with  trenails  or  spikes  to  it  about  3  ft.  from  each  end. 
The  log  is  then  pushed  off  a  little,  a  second  log  brought  up  under 
the  transoms  and  in  close  contact  with  the  first.  The  second  log 
is  then  spiked  like  the  first,  and  so  on  for  each  remaining  log. 
Care  must  be  taken  to  place  the  whistle  ends  up  stream  with  the 


PLATE  45. 


PLATE  46. 


PLATE    47. 


PLATE    48 


Floating  Bridges.  163 

bevel  underneath,  and  to  spike  the  transoms  perpendicular  to  the 
logs.  If  the  stream  is  very  gentle,  the  up-stream  ends  of  the  logs 
need  not  be  placed  as  in  Fig.  5,  but  may  be  parallel  to  the 
transoms. 

Another  metJiod  is  to  lash  the  logs  together  and  fasten  on  the 
transoms  with  spikes  or  trenails.  Or,  lash  the  logs  together  and 
lash  the  transoms  to  the  logs,  tightening  the  lashings  with  rack 
sticks. 

339.— Two  additional  transoms  should  be  placed  on  the  raft 
by  whatever  method  employed  in  putting  on  the  first.  They 
should  be  the  distance  of  the  roadway  or  platform  apart,  at  equal 
distances  from  the  center  of  gravity  of  the  raft,  and  bear  upon  all 
the  logs.  In  order  to  obtain  sufficient  buoyancy,  and  allow  suf- 
ficient water  way,  several  courses  of  timber  may  have  to  be  em- 
ployed. For  use  in  a  bridge,  a  raft  should  have  an  available 
buoyancy  of  15,000  lbs. 

340.— If  the  raft  is  to  be  used  as  a  flying  bridge,  it  should  have 
the  shape  of  a  lozenge.    (PI.  43,  Fig.  8.) 

341.— Anchors.  Anchors  for  the  U.  S.  Advance  Guard  Bridge 
Train  weigh  75  lbs.,  and  for  the  Reserve  Train  150  lbs.  These 
will  be  sufficient  for  moderate  streams.  An  anchor  with  the 
names  of  the  various  parts  Is  shown  in  PI.  45,  Fig.  1. 

342.— The  distance  of  the  anchor  from  the  bridge  should  be 
at  least  10  times  the  depth  of  the  stream;  otherwise  the  bow  of 
the  boat  or  ponton  will  sink  too  deep  in  the  water.  The  direction 
of  the  cable  must  be  the  same  as  the  current.  The  anchor  cable 
should  be  of  1  in.  rope  and  attached  to  the  anchor  ring  by  a  fish- 
erman's bend.  A  buoy  might  be  attached  to  the  anchor  by  means 
of  a  i/^-in.  breast  line,  in  order  to  mark  its  position  and  serve  as 
a  means  of  raising  it.  The  breast  line  is  attached  to  the  buoy 
ring  by  a  fisherman's  bend  and  round  the  shank  of  the  anchor, 
close  to  the  crown,  by  a  clove  hitch. 

343.— The  number  of  anchors  will  depend  on  the  strength  of 
the  current.  It  is  generally  sufficient  to  cast  an  anchor  up-stream 
for  every  alternate  boat  or  ponton,  and  lialf  that  number  down- 
stream. If  the  stream  is  rapid,  every  boat  should  be  anchored 
up-stream. 

If  very  rapid,  the  bridge  must  be  secured  to  a  hawser,  as  shown 
In  PI.  46,  Fig.  1.      If  the  bridge  is  short,  ropes  can  be  stretched 


164  Floating  Bridges. 

from  the  piers  to  the  banks.  (Fig.  2.)  If  anchors  are  scarce,  one 
may  be  attached  to  two  piers.    (Fig.  3.) 

Before  being  cast,  the  anchor  should  be  well  stocked.  Rafts 
of  casks  or  timbers  bring  a  greater  strain  on  anchors  than  boats 
or  pontons. 

344.— Substitutes  for  Anchors.  One  or  two  spare  wheels 
with  tires  and  felloes  removed.  (PI.  45,  Figs.  3  and  4.)  Two  or 
more  pick-axes,  laid  together  or  fixed  on  one  handle.  (PI.  46,  Fig. 
4.)  A  harrow  with  lengthened  teeth,  loaded  with  stones.  Ga- 
bions filled  with  stones.  Large  stones  or  railway  irons.  Nets 
filled  with  stones.    Frame  filled  with  stones.    (PI.  45,  Fig.  2.) 

Care  must  be  taken  to  allow  the  anchor  to  fall  in  good  holding 
ground.  For  this  purpose,  a  direction  oblique  to  the  current  may 
sometimes  be  allowed. 

345.— Forming  Floating  Bridges.  Floating  bridges  may 
be  formed  in  the  following  ways:— 

(1)  By  successive  pontons  or  boats. 

(2)  By  parts. 

(3)  By  rafts. 

(4)  By  conversion. 

346.— By  Successive  Pontons.  (PI.  49.)  This  may  be  done 
in  two  ways:— 

(1)  By  adding  to  the  head  of  the  bridge,  the  tail  being  station- 
ary. This  method  requires  the  roadway  material  to  be  carried  an 
increasing  distance.  The  men,  however,  do  not  have  to  work  in 
the  water. 

(2)  By  adding  to  the  tail  of  the  bridge,  the  head,  already  con- 
structed, being  constantly  pushed  into  the  stream.  The  materials 
do  not  have  to  be  carried  so  far  as  in  the  first  case,  but  it  requires 
a  number  of  men  to  work  in  the  water  and  Is  not  advantageous 
where  the  bank  is  steep. 

In  the  first  method,  those  boats  or  pontons  which  cast  up- 
stream anchors  should  be  moored  above  the  approach  to  the 
bridge,  the  others  below. 

347.— By  Parts.  (PI.  49.)  In  this  method,  the  boats  or  pon- 
tons are  brought  close  to  the  shore  above  the  bridge.  For  con- 
venience in  putting  the  parts  together  several  chess  are  laid  from 
the  bank  to  the  interior  gunwale  of  one  boat  or  ponton.  The 
boats  or  pontons  forming  the  part  are  then  brought  in  place  and 


PLATE -49. 


166  Floating  Bridges, 

balks  placed  on  them.  The  chess  forming  the  roadway  are  then 
placed  on  the  balks,  excepting  a  sufficient  number  at  each  end  of 
the  part  to  allow  for  the  insertion  of  a  bay  between  the  parts. 
The  parts,  all  constructed  as  dh-ected,  are  then  placed  in  position, 
each  part  carrying  enough  material  to  construct  the  connecting 
bay.  The  parts  are  joined  with  each  other  and  with  the  abut- 
ment bay,  which  has  been  previously  constructed. 

348.— By  Bafts.  Each  raft  formed  of  2  or  more  piers  is  con- 
structed complete  and  the  rafts  come  into  the  bridge  in  succes- 
sion. Each  of  the  methods,  bridge  by  raft  and  bridge  by  parts, 
has  the  advantage  of  simultaneously  employing,  a  large  number 
of  men.    (PI.  49.) 

349.— By  Conversion.  (PI.  49.)  In  this  method,  the  bridge 
is  put  together  entire  along  the  shore  above  the  selected  site.  A 
tributary  stream  may  be  advantageous  for  this  purpose.  The 
bridge  is  then  floated  toward  the  site,  care  being  taken  to  prevent 
the  pivot  end  from  touching  the  shore  and  the  wheeling  end  from 
turning  too  fast. 

350.— The  various  methods  above  described  may  be  combined 
in  the  construction  of  one  bridge. 

The  connection  of  the  bridge  with  the  shore  may  be  made  by 
allowing  the  balks  to  rest  on  an  abutment  sill  let  about  1  ft.  into 
the  ground,  or  by  a  trestle. 

351.— If  the  stream  is  to  remain  ojieu  to  traffic,  it  is  well  to 
liave  two  or  more  rafts  in  mid-stream,  arranged  to  swing  so  as  to 
allow  boats  to  pass,  or  the  halves  of  the  bridge  may  be  swung  for 
this  purpose.  Usually  the  passage  is  made  by  allowing  the  rafts 
or  halves  to  swing  with  the  current;  they  are  then  brought  back 
against  the  current. 

352.— Floating  Objects.  Some  arrangement  should  be  made 
to  protect  the  bridge  from  floating  objects.    This  mav  be  done:— 

(1)  By  a  guard  of  observation,  stationed  above  the  bridge,  pro- 
vided with  boats  containing  anchors,  grapnels,  hammers,  chains, 
etc.  The  object  may  be  turned  ashore,  or,  if  this  is  not  possible, 
an  anchor  may  be  attached  to  it  to  break  its  momentum. 

(2)  By  a  floating  stockade,  constructed  of  trees  united  by 
chains  and  forming  a  continuous  barrier  to  floating  objects.  Its 
direction  should  be  about  20°  with  the  current. 

(3)  By  constructing  the  bridge  by  rafts  and  withdrawing  the 
menaced  part,  thus  allowing  the  object  to  float  past. 


Floating  Bridges. 


167 


352a. — Improvised  Floating  Bridge.*  A  practical  improvised 
floating  bridge  having  a  wagon-road  10  ft.  wide  was  constructed 
at  Molo,  Island  of  Panay,  P.  I.,  across  a  tidal  stream  300  ft.  wide, 
and  is  described  as  follows: 

Floating  piers  at  intervals  of  10  ft,  consisting  of  bundles  of 
25  bamboo  poles  ("a"),  supported  the  roadway,  which  consisted 
of  a  mat  of  interwoven  bamboo  strips  ("b")  resting  on  a  bamboo 
corduroy  ("c"),  which  in  turn  rested  on  four  hard  wood  balks, 
2l^  in.  X  4  in.  in  cross-section  ("d").  Rattan  lashings  were  used 
throughout  and  aprons  were  improvised  at  the  shore  ends  of  the 
bridge  to  allow  for  the  3-ft.  rise  and  fall  of  the  tide. 


In  anchoring,  advantage  was  taken  of  the  piles  of  a  former 
bridge,  as  shown  in  sketch.  The  bamboo  crib  ("e"),  built  loosely 
around  the  pile,  rose  and  fell  with  the  tide  and  prevented  the 
bridge  from  floating  either  up  or  down  stream.  The  buoyancy  of 
this  bridge  was  such  that  infantry  in  column  of  fours  did  not 
bring  the  balks  into  the  water. 


♦This  bridge  was  constructed,  using  native  labor,  by  Captain  B.  F.  Cheatham,  Q. 
M.  U.  S.  Array,  in  June,  1899,  and  was  still  in  use  a  year  later. 


CHAPTER  XVII.— Roads. 

353.— The  frequent  necessity,  in  the  field,  for  the  construction 
of  a  short  piece  of  road,  or  the  repairing  of  existing  roads,  malves 
it  important  that  all  who  may  at  any  time  have  this  worli  in 
charge  should  be  familiar  with  the  principal  requirements  of  it. 

354.— Two  desirable  conditions  in  a  road  are  that  it  be  straight 
and  level;  where  both  cannot  be  obtained,  straightness  is  sacri- 
ficed to  levelness.  Other  things  being  equal,  the  length  of  a  road 
may  often  be  advantageously  increased  20  ft.  for  every  foot  of 
vertical  height  avoided. 

355.— Limiting  Gradient.  As  levelness  cannot  always  be  ob- 
tained, various  considerations  fix  limits  for  the  steepness,  called 
limiting  gradients,  which  are  to  be  used  only  when  unavoidable; 
thus,  for  a  very  short  distance,  as  an  approach  to  a  bridge,  the  lim- 
iting gradient  may  be  1-10;  a  grade  of  1-12  should  not  exceed  100 
ft.;  one  of  1-15  should  not  exceed  200  ft.;  1-20  should  ordinarily  be 
the  limiting  gradient  for  easy  travel,  while  1-30  to  1-35  is  still 
better. 

356.— Compared  to  what  he  can  draw  on  a  level,  a  horse  can 
draw  only  about  90  per  cent  on  a  grade  of  1-100,  80  per  cent  on 
1-50,  50  per  cent  on  1-24,  and  25  per  cent  on  1-10,  but  for  a  short 
distance  he  can  exert  6  times  his  ordinary  force. 

357.— A  road  should,  if  possible,  always  rise  continuously  to 
its  highest  point  and  nowhere  descend  partially  again. 

358.— Width.  For  military  purposes  roads  should  be  wide 
enough  to  allow  wagons  going  in  opposite  directions  to  pass  each 
other  easily;  this  is  usually  taken  at  16  ft.  For  wagons  going  in 
one  direction  only  or  with  turnouts  at  intervals,  and  for  Infant- 
ry in  column  of  fours,  or  cavalry  in  column  of  twos,  9  ft.  will  suf- 
fice, and  for  pack  animals  6  ft.  At  turns  in  a  zig-zag  road  up  a 
hill  the  road  should  be  level  and  the  width  increased  from  %  to  %. 

359.— Form.  The  best  for  the  upper  surface  is  that  of  two 
planes  inclined  at  an  angle  of  about  1-24  and  joined  by  a  slight 
curve  5  ft.  long.    (PI.  50,  Figs.  1,  2  and  13.) 

Between  the  road  and  ditches  should  be  flat  mounds  raised  6 
in.  or  more  above  the  surface,  with  sloping  sides  covered  with 
sods  or  stone  next  to  road,  forming  with  roadway  the  gutters: 


Sub'Q  drain  SubOcfraJr, 


£arth  sides 


Metal  Center  ■^"''^''  -^^^^s 


170  Roads. 

they  serve  also  to  hold  up  the  road  material  and  as  warnings  at 
night  of  the  proximity  of  the  ditch. 

On  the  hillside  the  surface  should  be  a  single  plane  inclined 
towards  the  hill.    (Figs.  3,  4,  5,  7  and  8.) 

360.— Road-bed.  The  surface  of  the  road-bed  should  be  dug 
out  or  built  up  and  solidly  compacted,  either  by  rolling  or  ram- 
ming, and  when  ready  to  receive  the  road  material  should  be  of 
the  same  shape  as  the  surface  of  the  finished  road,  with  shoulders 
at  the  sides  to  retain  the  material  in  place.    (Fig.  13.) 

On  hillsides  of  gentle  slope,  the  road-bed  is  usually  made  of 
half  cutting  and  half  filling,  the  lower  side  of  the  slope  being 
stepped  to  retain  the  earth  excavated  (Fig.  3);  on  steep  slopes  it 
is  often  necessary  to  both  step  the  slope  and  build  a  retaining 
wall  of  stone  (Fig.  4),  or  of  logs  (Fig.  5),  or  of  other  materials;  on 
very  steep  slopes  it  may  be  necessary  to  build  retaining  walls  on 
both  sides  (Fig.  7);  while  in  rocky  formations  the  excavated  hill- 
side may  be  left  nearly  vertical.     (Fig.  8.) 

361.— Drainage.  Nothing  is  of  greater  importance  in  road- 
building  than  proper  drainage.  It  is  the  life  of  a  road.  In  a 
level  country  it  is  necessary  to  raise  the  road-bed  to  keep  it 
always  free  from  water.  None  must  be  allowed  to  remain  on  the 
surface  and  all  must  be  drained  from  beneath.  To  accomplish 
this -ditches  must  be  dug  on  both  sides  of  a  road  on  level  ground 
and  in  cuttings,  from  2  to  3  ft.  below  the  road-bed  and  of  a  width 
depending  on  the  amount  of  water  to  be  discharged.  (Figs.  1 
and  2.)  In  wet  places,  low-lying  lands,  clayey  and  springy  soils, 
the  ditches  must  be  deeper  and  sub-drains  3  to  5  ft.  below  the 
road,  emptying  at  intervals  into  the  side  ditches,  must  be  made  to 
keep  it  dry.    (Fig.  1.) 

Rain  falling  on  the  surface  of  the  road  is  collected  in  the  gut- 
ters on  the  sides  and  run  into  the  side  ditches  by  drains  at  fre- 
quent intervals. 

On  a  hillside,  between  the  road  and  the  hill  is  the  ditch,  from 
which  the  water  is  discharged  through  culverts  or  covered  drains 
under  the  road  into  the  natural  watercourses.  Catch  drains 
along  the  top  of  the  cutting  are  made  to  prevent  the  slopes  being 
washed  down  and  the  water  from  above  finding  its  way  to  the 
road, 


Roads.  1*71 

Wlieie  open  ditches  are  liable  to  become  filled,  some  kind  of 
covered  drain  must  be  used.    (Figs.  5,  10,  11  and  12.) 

Tiieoretically,  a  road  should  be  perfectly  level,  but  for  pur- 
poses of  drainage,  in  the  direction  of  its  length,  it  should  have  at 
least  a  slope  of  1-125. 

On  a  steep  road,  shallow  paved  water  tables  extending  oblique- 
ly across  the  road  are  sometimes  necessary  to  catch  the  water 
running  down  the  road  and  carry  it  to  the  gutters,  or  small 
mounds  crossing  the  road  obliquely  are  substituted.    (Fig.  9.) 

362. — The  surface  of  a  road  ought  to  be  as  smooth  and  as  hard 
as  possible,  for  which  purpose  various  liinds  of  covering  material 
are  put  on  the  bed. 

As  the  road-bed  must  be  kept  thoroughly  dry  at  all  times  by 
the  ditches  intercepting  all  ground  water,  so  the  stone  or  other 
covering  must  be  so  thoroughly  rolled  and  compacted  that  no 
water  falling  upon  the  surface  can  possibly  find  its  way  down  to 
the  foundation  and  through  it  to  the  bed. 

363.— When  roads  are  made  of  broken  stone  the  material  in 
the  Telford  class  is  composed  of  two  parts:  the  foundation  and 
the  covering.  (Fig.  1,  right  half.)  The  foundation  consists  of 
a  uniform  thickness  of  not  less  than  5  in.  of  any  durable  broken 
stone  with  bases  about  5  in.  x  10  in.  laid  close  together  by  hand, 
larger  faces  down,  firmly  wedged  with  smaller  stones  in  the  in- 
terstices, and  the  whole  sledged  and  rolled  to  a  uniform  sur- 
face. Then  a  thin  layer  of  binding  material,  as  clay  or  loam,  is 
sprinkled  over  it  and  rolled.  On  this  is  put  the  covering,  consist- 
ing of  a  layer  of  about  3  in.  of  broken  stone  of  uniform,  well- 
shaped  cubical  pieces  which  will  pass  through  a  ring  from  2  to 
21^  in.  in  diameter,  and  rolled  to  a  uniform,  compact  surface. 
Then  another  layer  of  binding  material  is  added  and  well  rolled. 
Another  layer  of  stones,  3  in.  thick,  of  sizes  from  1  to  2  in.  in  diam- 
eter, is  next  spread  and  rolled  as  before.  On  this  may  be  spread 
another  binding  coat,  well  rolled,  then  a  thin  layer  of  fine  screen- 
ings or  fine  gravel  free  from  dirt.  Often,  where  traffic  is  light 
and  expense  large,  a  single  layer  of  broken  stone  4  in.  thick  is  put 
on  the  foundation. 

364.— In  the  Macadam  class  (Fig.  1,  left  half)  the  hand-laid 
foundation  is  not  used,  but  generally  three  layers,  each  from  3  to 


^Td  Roads. 

-k  m.  Liiick,  ui  biuJieu  biune  and  bmdiiig  cout«,  as  described  abuve, 
are  spread  aud  rolled  until  smoota  and  compact. 

For  light  trallic  a  single  layer  ot  4  in.  is  sometimes  used. 

365.— Tlie  best  stone  is  a  compact,  tine-grained  syenite,  basalt 
or  trap  rock.  Hornblend,  actinolyte,  dioryte,  and  some  other 
rocks  make  good  material.  Quartz  and  flint,  though  very  hard, 
are  brittle,  ditflcult  to  work,  and  not  so  good.  Granite,  on  ac- 
count of  mica  in  it,  breaks  up  and  grinds  away  too  easily.  Gneiss 
is  poorer  than  granite.  Slatey  rocks  generally  break  up  too  eas- 
ily. Limestone,  generally  too  soft,  grinds  away  easily,  making  a 
very  disagreeable  dust.  Softer  stones  may  be  used  for  the  foun- 
dations and  lower  layers,  but  only  the  hardest  and  toughesi 
should  be  used  for  the  coverings. 

366.— Earth  roads  require  even  greater  care  in  draining,  grad- 
ing, and  forming  the  surface  than  those  described,  and  a  trans- 
verse slope,  not  less  than  1-20,  to  hasten  the  flow  of  surface  water 
to  the  gutters.  No  sods  or  vegetable  refuse  should  be  allowed  in 
grading  or  filling  ruts,  only  gravelly  earth,  if  obtainable. 

Roads  are  frequently  made  with  a  metal  portion  in  the  center 
and  earth  roads,  called  wings,  on  the  sides.    (Fig.  2.) 

367.— It  is  almost  impossible  to  construct  a  road  of  clay  which 
will  be  good  in  wet  weather,  but  a  very  sandy  road  may  be  im- 
proved by  working  a  little  clay  in  it. 

368.— For  gravel  roads  the  bed  is  first  formed  as  described. 
The  gravel  is  screened  to  remove  stones  larger  than  2%  in.  in 
diameter  and  such  as  are  less  than  %  in.;  and  all  earthy  matter. 
A  layer  of  the  screened  gravel,  4  or  5  in.  thick,  is  then  spread  and 
rolled,  then  another  layer  of  3  or  4  in.,  which  should  also  be  well 
rolled. 

869.— Repairs.  Ruts  appearing  should  be  immediately  filled 
in,  and  traffic  directed  over  all  parts  of  road  Before  spreading 
stones,  all  mud  should  be  cleaned  off  and  the  surface  picked  up  a 
little  to  allow  the  new  stone  to  bind  into  the  old,  wet  weather  be- 
ing preferred,  or  the  stones  should  be  sprinkled.  Ditches  and 
culverts  must  be  cleaned  as  needed. 

370.— In  crossing  marshy  ground  that  cannot  be  well  drained, 
corduroy  roi4s  made  of  logs  of  suitable  lengths  laid  side  by  side 
across  the  road,  over  which  is  spread  a  covering  of  earth  or  gravel, 
are  sometimes  used. 


Roads.  173 

371.— Brushwood,  made  into  fasciues  and  hurdles,  may  be 
used  the  same  way  as  a  foundation.  With  fascines,  the  top  row 
should  extend  across  the  road  and  be  of  a  length  equal  to  the 
width  of  road.    (Fig.  6.) 

372.— Where  lumber  is  the  cheapest  material,  plank  roads  may 
be  built  by  first  laying  parallel  rows  of  sleepers  or  sills  flush 
with  the  ground,  about  4  ft.  apart,  in  the  direction  of  the  road,  on 
which  boards,  3  in.  thick  by  9  to  12  in.  wide  and  8  ft.  long,  are 
placed  crosswise. 

373.— The  construction  of  communications  to  all  parts  of  a 
position  to  facilitate  the  movement  of  troops,  etc.,  from  one  part 
to  another,  is  almost  always  a  certain  necessity.  These  would 
rarely  be  more  than  temporary,  but,  if  made  on  the  lines  indi- 
cated, as  far  as  time  and  requirements  permitted,  so  much  the 
better. 

374.— Roads  and  paths  may  have  to  be  cleared  through  woods; 
wet  places  made  passable  by  corduroying  or  filling  up  with  brush, 
fascines,  etc.;  and  approaches  made  to  ascend  steep  places. 

Wherever  roads  cross  or  separate,  signs  should  be  put  up  tell- 
ing exactly  where  each  leads. 


PLATE  51 


FIG.l 


FIG.2. 


Pi.ATm 


a      a      D      D      D      D 


FIGS.       /fartfrrd  fl-esaed^eeim.  FIG  5: 


FIG.  4. 


FIG6. 


^f^m       V 


w 


FIGS. 


IntfrUtkingiolis  FIG  7 

Fiaa 


I 


BRIOCE  RAIL  JOfff] 


FIG;10. 

n.  m.m.m M. 


Em 


Crossing 

FIG.12. 


CHAPTER  XVIIi.— Railroads. 

375.— In  military  operations,  the  principal  duties  of  troops  in 
connection  with  railroads  will  be  either  ther  repairing  of  lines  that 
have  been  partially  destroyed,  or  the  destruction  of  lines  to  pre- 
vent their  use  by  the  enemy. 

376.— A  railroad,  as  existing  in  its  completed  form,  will  be 
briefly  described  to  indicate  the  state  to  which  it  should  be 
brought  hy  repairs  after  destruction,  and  to  so  familiarize  one 
with  it  as  to  suggest  methods  of  most  effectually  destroying  it. 

377.— A  railway  line  consists  of  a  series  of  straight  lines  of 
different  lengths,  called  tangents,  which  are  joined  by  curves. 
The  road-bed  is  first  prepared  with  a  smooth  hard  surface  (slop- 
ing slightly  from  the  middle  to  each  side  for  drainage)  from  10  to 
12  ft.  wide  for  a  single  track,  and  from  21  to  25  ft.  for  a  double 
track.  On  this  is  placed  the  ballast,  from  12  to  24  in.  thick,  of 
broken  stone,  gravel  or  cinders,  etc.,  for  the  pui-pose  of  distribut- 
ing the  load  over  a  larger  surface,  holding  the  ties  in  place,  carry- 
ing off  the  rainwater,  affording  a  means  of  keeping  the  ties  up  to 
grade  line  and  giving  elasticity  to  the  road-bed. 

378.— The  ties  are  generally  of  wood,  hewn  flat  on  top  and 
bottom,  from  7.5  to  9  ft.  long,  6  to  10  in.  wide,  and  about  7  in. 
deep.  It  is  customary  to  sink  them  about  half  their  depth  into 
the  ballast.  Their  object  is  to  hold  the  rails  in  place  and  furnish 
an  elastic  medium  between  the  rails  and  ground.  The  distance 
apart  is  usually  2.5  ft.  from  center  to  center,  but  depends  upon 
weight  of  engines  and  strength  of  rails.  They  should  be  uni- 
formly spaced  to  distribute  the  weight  equally. 

Tie  plates  (PI.  51,  Figs.  3  and  7)  are  often  used  to  prevent  the 
rails  from  crushing  into  the  ties. 

379.— Tests  of  metal  ties  in  the  interests  of  economy  and  eflS- 
ciency  have  been  made  with  satisfactory  results.  On  some  level 
portions  of  the  N.  Y.  Central  R.  R.  are  used  the  Hartford  pressed 
steel  tie  (Figs.  1  and  2),  to  which  the  rails  are  fastened  by  clamps 
bolted  to  the  tie. 

380.— The  form  of  rail  used  in  the  United  States  is  shown  in 
Fig.  3,  being  the  "T"  rail,  which  varies  in  weight  from  12  to  100 
lbs.  per  yard.  The  mean  dimensions  of  80  lb.  rails  are  given  on 
wi2- 


1^6  Railrodda. 

left-hand  side  of  figure  and  of  100  lb.  rails  on  right-Land  side. 
They  are  placed  3  ft.  apart  for  narrow  gauge,  4  ft.  8.5  in.  for 
standard  gauge,  while  6  ft.  is  the  broadest  gauge  in  the  United 
States,  measured  from  inside  to  inside  of  head.  The  tops  of  rails 
must  be  slightly  inclined  to  fit  the  cones  of  the  wheels. 

381.— The  weak  part  of  a  track  is  at  the  joints.  The  old 
method  of  using  chairs  under  the  ends  of  rails  has  about  ceased, 
the  practice  now  being  to  fish  the  joints  by  plates  (Fig.  1),  and 
angle  irons.  (Fig.  3.)  Tliere  are  also  used  what  are  known  as 
the  Reinforced  rail  joints  (Fig.  4),  Bridge  rail  joints  (Fig.  8),  Dou- 
ble Girder  rail  joints.    (Fig.  9.) 

382.— Rails  are  fastened  to  the  ties  by  spikes,  the  best  being 
made  with  sharp,  chisel-edge  points,  clean,  sharp  edges,  and 
smooth  surfaces,  so  as  to  cut  and  press  aside  the  fibers  of  the 
wood,  instead  of  tearing  them.  Attempts  to  increase  the  hold- 
ing power  by  jagged  or  twisted  spikes  have  been  unsuccessful. 
On  bridges,  interlocking  bolts  (Fig.  6)  are  much  used  instead  of 
spikes.  To  keep  the  track  in  the  right  line,  allowance  must  be 
made  for  the  contraction  and  expansion  of  the  rails,  by  not  plac- 
ing them  in  contact  at  the  joints,  and  the  holes  for  the  bolts  must 
be  elongated. 

383.— The  centrifugal  force  of  a  train  passing  around  a  curve 
tends  to  throw  the  wheels  against  the  outer  rails,  which  is  par- 
tially counteracted  by  raising  them  to  throw  the  center  of  gravity 
inward  and  cause  the  car  to  slide  inward.  Each  rail  in  a  curve 
ought  to  be  bent  to  fit  the  curve  before  being  laid. 

384.— On  single  tracks,  there  are  laid  at  occasional  intervals 
short  pieces  of  track,  called  sidings,  to  enable  trains  to  pass  one 
another.  The  arrangement  for  passing  from  one  track  to  another 
is  the  switch,  which  consists  of  a  single  length  of  rails,  movable  at 
one  end  by  a  lever,  so  as  to  connect  with  either  pair  of  rails.  The 
simplest  form  is  the  stub  switch  (Fig.  10),  which  leaves  one  line 
always  open  while  the  other  is  continuous.  The  one  in  common 
use  is  the  split  or  point  switch.  (Fig.  11.)  Various  devices  are 
used  for  locking  and  interlocking  switches,  to  avoid  accidents. 
At  the  points  where  the  inner  rails  cross  is  placed  a  frog  (PI.  52, 
Fig.  1),  which  enables  the  wheels  to  pass  over  the  inner  rail  of 
the  other  track. 


PLATE  52. 


FIGl 


FrG:8. 


f/4- 


178  Railroads. 

385.— Orosbiugjs  occur  where  two  tracks  intersect,  and  consist 
of  four  frogs  and  corresponding  guard  rails.    (PI.  51,  Fig.  12.) 

386.— Wliere  one  main  line  passes  to  another  is  called  a  junc- 
tion and  the  ordinary  switch  is  used.  In  crossing  from  one  track 
to  a  pai'allel  track  the  rails  are  arranged  as  in  PI.  52,  Fig.  2. 

387.— A  wye,  from  a  similarity  to  the  letter  "Y,"  is  an  arrange- 
ment of  tracks  for  turning  around  engines  and  cars  and  connect- 
ing cross-roads.    (Fig.  3.) 

388.— Turntables  are  platforms,  turning  on  rollers  upon  an 
underground  circular  track,  used  to  transfer  engines  and  cars 
from  one  track  to  another  and  to  turn  them  around. 

389.— The  locomotive  engine  is  the  power  on  railroads.  They 
weigh  up  to  232,000  Ihs.  without  tender,  and  to  292,000  lbs.  for 
passenger  to  365,000  lbs.  for  freight,  with  tender,  and  draw  2,400 
or  more  tons  on  a  level.  The  amount  of  coal  consumed  being  from 
40  lbs.  to  70  lbs.  per  mile  run. 

390.— The  rolling  stock  consists  of  passenger  cars  for  about  60 
persons,  48  to  52  ft.  long,  9.5  ft.  wide,  w  eighing  from  40,000  lbs. 
to  G0,000  lbs.;  sleeping  cars  for  64  passengers,  60  to  70  ft.  long, 
9.8  ft.  wide,  weighing  60,000  lbs.  to  90,000  lbs.;  mail,  express  and 
baggage  cars,  45  ft.  long,  9.3  ft.  wide,  weighing  about  27,000  lbs.; 
freight  cars  consist  of  Box,  Refrigerator,  Hay,  Furniture,  Oil, 
Stock,  etc.,  and  are  about  34  ft.  long,  8.5  ft.  wide,  weighing  from 
20,000  lbs.  to  30,000  lbs.,  capacity  20  to  30  tons;  flat  cars,  34  ft.  long, 
weighing  16,000  lbs.  to  19,000  lbs.  Height  of  top  of  box  cars  above 
rails  about  15  ft.  Freight  cars  are  being  rapidly  provided  with  the 
M.  C.  B.  automatic  couplers.     (Fig.  4.) 

391.— The  buildings  consist  of  passenger  and  freight  depots, 
engine  houses,  fuel  sheds,  water  tanks,  repair  shops,  and  section 
houses.  At  convenient  points  are  generally  located  yards  where 
stock  can  be  loaded  and  unloaded.  It  may  sometimes  be  neces- 
sary, however,  to  load  and  unload  animals  and  supplies  in  the 
field  along  a  railroad  where  there  are  no  platforms  or  other  con- 
veniences, which  must  then  be  built. 

392.— A  simple  form  of  ramp,  in  the  absence  of  anything 
better,  could  be  made  by  taking  3  or  4  planks  3  in.  thick,  10  to  12 
in.  wide,  and  10  to  14  ft.  long,  fastening  them  together  side  by 
side,  preferably  by  footholds  nailed  across  on  top  and  several 
cleats  on. the  bottom;  otherAvise,  by  lashing,  wiring  or  by  stakes 


Railroads.  179 

at  the  bottom  when  in  position,  and  we9ges  in  the  car  door.  The 
ends  on  the  .s^round  should  be  slightly  sunken  and  rested  against 
a  cross  beam.  Ropes  should  be  hung  along  the  sides  and  blankets 
or  canvas  hung  on  them.  Props  of  some  kind,  as  sacks  of  grain, 
bales  of  hay,  etc.,  can  be  placed  under  the  middle  to  strengthen 
it  if  necessary. 

393. — Another  form  of  portadU  rarnp,  which  could  be  carried 
on  all  railroad  trains  where  they  might  be  needed,  consists  of  6 
long  timbers  4  in.  x  4  in.  x  14  ft.,  6  short  timbers  4  in.  x  4  in.  x  6 
ft.,  24  boards  1.5  in.  x  12  in.  x  6  ft.  with  footholds  nailed  length- 
wise on  one  side. 

To  load  or  unload  horses,  rest  the  ends  of  three  or  four  of  the* 
long  timbers,  equally  spaced,  on  the  car  floor,  the  other  ends  resting 
against  a  short  timber,  sunk  in  the  ground  and  staked  down.  On 
these  place  the  boards  forming  the  floor;  on  each  side  of  the  ramp, 
on  the  boards,  lay  a  long  timber  and  fasten  the  ends  to  the  timbers 
underneath.  The  boards  should  have  cleats  on  under  side  to 
prevent  slipping  sideways.  If  necessary,  some  of  the  remaining 
boards  can  be  set  edgewise  between  posts  of  the  short  timbers 
as  an  Intermediate  support. 

394. — To  unload  a  number  of  cars,  enough  men  can  be  placed  un- 
der the  ramp,  near  the  car,  to  raise  it  high  enough  to  allow  the  car 
to  be  removed  and  another  run  in  place,  thus  avoiding  taking 
the  ramp  apart  for  each  car. 

S95— -Semi-permanent  platforms  and  ramps  may  be  made  as  in 
Figs.  6  and  7,  if  rails  and  boards  are  available. 

396.— To  load  or  unload  tcagons  and  guns  from  a  flat  car,  place 
the  ramp  against  one  end  (Fig.  8),  using  four  long  timbers  for 
stringers  on  which  the  boards  are  placed,  the  other  two  long  tim- 
bers being  used  for  side  rails.  Support  underneath  with  boards 
set  on  edge,  held  between  some  short  timbers,  or  with  bales  of 
hay,  sacks  of  grain  or  otherwise,  as  necessary.  A  couple  of 
boards  can  be  used  to  run  the  wheels  from  the  car  on  to  the  ramp 
and  others  at  the  foot  of  ramp  to  carry  the  wheels  across  the  rails. 
The  lower  ends  of  the  stringers  should  abut  against  a  tie,  if  pos- 
sible: if  not,  they  should  be  staked  down. 

397.— PI.  53  is  a  design  of  a  portable  ramp  devised  by  Major 
E.  G.  Fechet,  6th  IT.  S.  Cavalry.  The  ramp  consists  of  7  boards 
1,5  Jp,  3C  T  J^«  ^  1?  ^t-  joined  together  In  three  sections  (2  for  the 


-  K 


Major  £.  C.Fschft, 

e"*^ Cavalry,  , 

US.At^Y, 


£.A.1^C.a: 


Railroads.  181 

outside,  "A,"  "A";  and  3  for  the  middle  one,  "B");  by  wooden 
strips  *'C,"  1  in.  thick,  and  2  in.  wide,  bolted  to  the  upper  surfaces, 
1  ft.  between  centers;  these  strips  also  serve  as  footholds.  Along 
the  middle  of  the  outside  boards  extends  a  side  rail,  "D,"  3  in.  x 
3  in.,  held  firmly  by  the  iron  straps,  "E,"  ^  in.  x  2  in.  On  the  out- 
side of  each  side  rail  are  3  sockets  *'F,"  for  standards  **G"  3  ft. 
high,  along  the  tops  of  which  are  to  be  stretched  ropes  or  chains 
from  which  canvas  or  blankets  are  hung.  On  the  under  side  of 
each  section  3  ft.  apart  are  bolted  iron  cleats,  "H,"  0.5  in.  x  2  in., 
beginning  at  18  in.  from  the  ends.  On  the  ends  of  each  section  are 
bolted  iron  claws,  "K,"  for  catching  the  car  floor  or  door  slide,  to 
prevent  slipping  when  in  position  for  use.  The  three  sections  are 
held  together  for  use  by  4  iron  tie  bars,  "L,"  0.5  in.  x  2  in.,  which 
are  placed  under  the  cleats  "H,"  and  the  whole  firmly  keyed  as 
shown.  This  form  of  ramp  may  be  made  longer  or  shorter,  nar- 
rower or  broader,  as  desired.  By  taking  out  the  standards  it  may 
be  hung  on  the  side  of  a  car  between  a  door  and  end.  It  is  easily 
taken  apart  and  transported  in  a  wagon,  and  as  easily  put  to- 
gether when  needed.  It  is  designed  to  combine  both  strength 
and  lightness.    It  weighs  about  400  lbs.  complete. 

398.— Disabling  and  destroying  railroads.  Under  the  head 
of  disahling  will  be  mentioned  means,  the  effects  of  which  will 
only  temporarily  interrupt  traffic,,  leaving  the  road  repairable  af- 
ter some  delay. 

399.— Under  destroying,  such  as  are  more  serious  in  their 
effects;  either  causing  extensive  repairs  or  a  change  of  route  to 
avoid  them. 

400.— The  disabling  of  railroads  will  usually  be  done  by  raid- 
ing parties  of  cavalry,  while  the  destroying  of  them  may  be  done 
by  such  parties  or  by  specially  detailed  troops  trained  for  such 
service. 

401.— It  must  be  understood  that  no  railroad  is  to  be  destroyed 
except  upon  the  orders  of  the  oflScer  commanding' In  the  field. 
If  otherwise,  and  It  should  be  taken  from  the  enemy,  the  dam- 
age done  might  seriously  embarrass  future  operations.  Before 
ordering  any  destruction  the  questions  will  arise — "Is  destruction 
absolutely  necessary?'*  "Will  it  be  of  no  further  use  and  is  every 
hope  of  regaining  it  gone?"  "Are  the  advantages  to  be  gained 
BulBcIent  to  compensate  for  the  damage  that  will  be  done?*   AW 


182  Railroads. 

the  attending  circumstances  should  be  carefully  considered,  es- 
pecially if  in  one's  own  country.  The  choice  of  points  for  de- 
struction and  the  most  effective  means  are  subjects  for  study.  It 
is  useless  to  destroy  anything  that  will  not  seriously  embarrass 
traffic. 

402. — A  railroad  may  be  disabled  by  removing  rails  at  vari- 
ous intervals,  then  destroying  or  hiding  them;  or,  if  a  large  num- 
ber of  men  are  at  hand,  select  a  high  embankment,  line  the  men 
along  on  one  side  of  the  track,  disconnect  the  rails  at  each  end  of 
the  line  of  men,  then,  at  a  signal,  they  raise  the  track  on  edge  and 
let  rails  and  ties  together  go  over  the  embankment.  Thus  treated, 
rails  and  ties  must  be  separated  before  being  replaced.  An  im- 
provised wrench  for  removing  nuts  on  fish-plates  is  a  bolt  with 
two  nuts  on  it,  just  far  enough  apart  to  grasp  the  nut  to  be  re- 
moved. (PL  52,  Fig.  5.)  If  time  is  an  object,  remove  outside 
rails  on  a  curve,  or  disconnect  a  joint  on  each  side  and  throw  them 
as  a  switch  to  derail  the  train  either  on  an  embankment  or  in  a 
cut,  or  use  explosives  as  described  in  Chap.  XX. 

By  laying  rails  across  a  pile  of  burning  ties  until  red  hot  in  the 
middle  they  may  be  easily  bent  around  a  tree  or  telegraph  pole; 
they  may  be  twisted  by  heating,  as  above,  then  using  bars  or  pick- 
axes placed  in  the  holes  in  each  end  and  working  in  opposite 
directions. 

They  may  be  torn  from  the  ties  and  twisted  cold  by  using  Gen. 
Haupt's  "TJ"-shaped  rail-twister,  shown  on  PI.  40,  Fig.  8.  Ten 
men  with  two  twisters,  two  axes,  two  stout  pieces  of  rope  35  ft. 
long,  can  tear  up  and  twist  a  rail  in  5  minutes.  The  junctions  of 
lines  are  important  points  to  attack  to  disable  a  track. 

Water  tanks  may  be  rendered  useless  for  a  time  by  breaking 
holes  in  them,  removing  pistons  from  pumps,  etc.  Fuel,  ties,  and 
small  bridges  may  be  burned.  Engines  may  be  disabled  by  burn- 
ing out  the  flues.  Temovirig  or  breaking  different  parts  of  the  ma- 
chinery, filling  suction  pipes  of  pumps  with  waste,  or  by  removing 
bolts  from  eccentric  straps,  etc.  Cars  may  be  disabled  by  removing 
couplers,  axle  boxes,  breaking  or  removing  trucks,  etc.  The  use 
of  mines  under  the  tracks,  so  arranged  as  to  be  exploded  by  the 
passing  of  trains,  is  an  effective  method  of  interrupting  traffic  and 
"shaking  the  morale  of  troops  being  transported. 

403,— To  destroy  a  railroad,  if  time  is  Bufflclpnt,  remove  roll- 


Railroads,  183 

ing  stock,  rails,  etc.,  to  the  rear.  Otherwise,  destroy  large  bridges, 
if  of  wood,  by  burning,  using  oil  if  it  can  be  obtained,  or  by  ex- 
plosives, as  in  Chapter  XX.;  if  of  iron,  steel,  or  masonry,  by  ex- 
plosives, as  in  Chapter  XX.  If  there  are  tunnels  on  the  line, 
select  longest  ones  and  blow  them  in  at  as  many  points  as  possi- 
ble, or  cause  two  wild  trains  to  collide  in  the  middle,  afterwards 
blowing  in  the  ends.  Those  with  sandy  soil  are  the  best.  Deep 
cuttings  with  retaining  walls  may  be  filled  in  by  use  of  explo- 
sives. If  trees,  poles,  wires,  etc.,  can  be  mixed  in— so  much  the 
better.  Blow  up  tanks  and  engines,  burn  all  fuel,  cars,  repair 
supplies,  etc.    Fire  a  cannon  ball  through  engines. 

404.— The  repair  of  railroads  will  best  be  accomplished  by 
a  construction  corps  having  some  of  the  elements  of  permanency 
in  its  organization;  or,  at  least,  by  small  squads  of  experienced 
men,  to  which  others  could  be  added  by  temporary  detail,  when- 
ever active  operations  require  such  increase.  They  should  be 
established  as  near  to  where  their  services  may  be  needed  as 
possible. 

405.— Bridges  should,  in  the  beginning,  be  classified  and  num- 
bered, so  that  a  single  reference  to  the  class  and  number  will  give 
complete  information  as  to  its  character,  dimensions,  etc.  At 
designated  points  will  be  kept  on  hand,  already  prepared  for  put- 
ting in  bridge,  suitable  materials  for  the  repair  of  each  class. 
This  was  done  by  the  Union  Army  from  1861  to  1865,  so  that, 
when  word  was  received  that  a  certain  bridge  had  been  destroyed, 
by  a  reference  to  the  class  and  number  the  reconstruction  corps 
started  out  carrying  with  it  just  what  was  needed  to  repair  the 
bridge.  Even  complete  trusses  for  the  larger  class  of  bridges 
were  prepared  and  kept  ready  for  use. 

406.— Tunnels  and  cuts  which  have  been  filled  up  can  gener- 
ally be  cleared  only  from  the  two  ends. 

407.— Rails,  fish-plates,  spikes,  ties,  etc.,  will  be  kept  in  store 
at  secure  places,  for  repairing  any  portions  of  destroyed  track. 
Rails  which  have  been  simply  bent  can  be  straightened  by  various 
means.  Gen.  Haupt's  method  was  as  follows:  Two  ties  were 
placed  on  the  ground,  across  these  two  more  ties'  and  on  top  a 
single  tie.  which  was  cut  across  one-half  the  depth  of  the  rail 
to  receive  It  and  prevent  It  turning.  Weight  was  applied  at  the 
two  ends  of  the  r^!l  hy  m^n  benrtngr  down  on  poles  placed  there^ 


184  Railroads, 

on.  The  rail  being  moved  back  and  forth  until  strai;?htened,  re- 
quiring from  4  to  5  minutes.  Rails  which  had  been  heated  and 
bent  to  a  very  sharp  angle  required  more  time,  necessitating  re- 
neating  and  hammering  until  straightened.  For  this  purpose,  at 
special  points,  were  prepared  furnaces  consisting  of  two  parallel 
walls  of  bricli,  stone  or  clay,  with  a  kind  of  grate.  The  straight- 
ening table  consisted  of  a  large,  square  timber  as  long  as  a  rail, 
on  which  were  securely  fastened  three  rails,  as  in  PI.  52,  Fig.  9, 
on  which  the  heated  rail  was  laid  and  hammered  until  straight- 
ened. Twisted  rails  require  rerolling  before  they  can  be  again 
used. 


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CHAPTER  XIX. -Telegraph  and  Telephone  Lines. 

408.— In  order  that  telegraphic  messages  may  be  sent  from 
one  point  to  another,  it  is  necessary  that  there  be  a  continuous 
metallic  conductor  from  the  first  to  the  second  point,  and  that 
this  conductor  be  insulated  from  contact  with  the  ground  or  with 
anything  leading  to  the  ground.  The  conductor  used  in  construct- 
ing permanent  lines  is  of  galvanized  iron  wire,  generally  of  size 
No.  9.  In  military  lines  it  is  generally  somewhat  smaller  on  ac- 
count of  the  weight,  and  sometimes  of  bare  copper  wire  about  No. 
14.  The  wire  is  carried  on  poles  and  tied  to  glass  or  other  insu- 
lators which  are  attached  to  the  poles. 

409.— Poles  should  be  not  less  than  22  feet  in  length  nor  less 
than  7  and  5  inches  in  diameter  at  the  larger  and  smaller  ends 
respectively,  but  may  be  as  much  longer  and  larger  as  de- 
sired, and  should  be  stripped  of  bark  and  pointed  at  the 
upper  end.  The  holes  for  poles  should  be  not  less  than  1-6  the 
length  of  the  pole  in  depth.  The  poles  should  be  raised  as  shown 
in  PI.  54,  Fig.  1,  and  held  vertically  while  the  excavated  earth  is 
thoroughly  tamped  in  from  bottom  to  top;  after  the  hole  Is  com- 
pletely filled,  the  earth  should  be  made  into  a  small  mound  so  as 
to  shed  water. 

410.— When  the  brackets  are  attached  to  the  pole  directly,  a 
seat  should  be  cut  !n  the  pole  with  a  hatchet  and  the  bracket 
should  be  nailed  on,  using  1  twenty-penny  and  1  forty-penny 
nail.  Where  the  poles  are  intended  to  carry  several  wires,  cross- 
arms  are  bolted  to  the  poles,  fitting  into  seats  cut  for  them.  The 
arms  carry  brackets  not  less  than  15  in.  apart.  The  arms  should 
not  be  less  than  20  in.  from  one  another.  Not  less  than  25  poles 
to  the  mile  should  be  used,  and  usually  the  number  is  increased 
to  30. 

411.— Every  5th  pole  should  be  protected  from  lightning  dis- 
charges by  having  a  piece  of  line  wire  run  from  about  6  in.  above 
tlie  tor>  of  the  r>ole  to  the  ground.  This  wire  must  be  so  arranged 
that  it  cannot  cf)me  in  contact  with  the  line  wire  should  that 
become  unfastened.  Poles  should  be  vertical  CTrept  when  nec- 
essary to  incline  them  to  resist  strain*?  when  they  will  be  set 
at  a  slight  inclination  in  such  manner  that  the  component  of 
the  strain  in  the  direction  of  the  length  of  pole  will  tend  to 
press  it  Into  the  ground,     Where  exppsefl  to  great  strains,  of 


Telegraph  and  Telephone  Limes.  187 

to  continuously  high  winds,  it  may  be  necessary  to  guy  the 
poles:  this  is  done  with  stays  consisting  of  two  or  more  line 
wires  twisted  together  and  fastened  near  the  top  of  the  pole,  the 
ground  end  being  attached  to  a  section  of  a  pole  or  timber  suita- 
bly anchored  in  the  ground,  as  shown  in  Fig.  2.  Where  possi- 
ble, the  line  of  poles  should  be  run  on  one  side  of  the  road  and 
far  enough  from  it  to  be  safe  from  accidental  damage  by  pass- 
ing wagons.  Where  roads  have  to  be  crossed,  the  wire  should 
be  carried  over  on  high  poles  so  as  to  clear  any  possible  wagon- 
load. 

412.— The  insulators  in  common  use  in  this  country  are  of 
glass  and  of  the  form  shown  in  IT'ig.  3.  The  one  shown  in  Fig.  4 
is  preferable,  as  it  is  not  so  liable  to  cause  leaks  on  account  of 
moisture  accumulating  and  forming  a  connecting  film  to  the 
bracket  and  from  that  to  the  pole. 

413.— The  wire  is  attached  to  the  insulators  by  pieces  of  wire 
called  ties.  These  are  generally  of  the  same  wire  as  the  .line. 
They  are  annealed  and  formed  on  an  insulator  and  cut  long 
enough  to  embrace  the  insulator  and  project  3  or  4  inches  beyond 
the  line  wire. 

414.— To  hang  the  wire.  The  wire  is  carried  up  to  the  top 
of  the  pole  and  the  lineman  places  a  tie  on  the  insulator,  the  line 
wire  against  the  insulator  above  the  tie  wire,  and  bends  the 
ends  of  the  tie  wire  upward  so  as  to  sustain  the  line  wire.  The 
line  wire  is  then  strained  by  the  lineman,  either  by  means  of 
hand  power  or  by  use  of  the  wagon  carrying  the  reel.  When 
the  line  wire  is  stretched  so  that  it  sags  but  about  V/o,  ft.  in  70 
yds.,  the  tie  wire  is  wrapped  around  it  about  one  and  a  half 
times,  finishing  with  the  ends  of  the  tie  wire  pointing  towards 
the  insulator;  this  secures  the  line  and  completes  the  work. 
(Fig.  5.) 

415. — ^In  open  country  the  line  wire  is  strung  on  the  insulator 
on  the  side  towards  the  pole,  so  that,  if  it  becomes  accidentally 
undone,  the  wire  will  not  drop.  If  in  timbered  country,  then 
hang  it  on  the  side  from  the  pole,  so  that  when  trees,  etc.,  fall 
against  the  wire  It  will  simply  tear  it  away  from  the  insulator, 
but  will  not  break  the  line  wire.  When  necessary  to  hang  the 
wire  on  trees,  a  regrular  tree  insulator  should  be  used,  and  in 
default  of  this,  the  tie  shown  in  Fig.  6  may  be  used,  the  ends 


188  Telegraph  and  Telephone  Lines. 

beiug  wound  loosely  jso  as  to  allow  of  an  easy  lateral  motion  to 
accommodate  the  swing  of  the  tree.  Tlie  poles  should  be  num- 
bered at  each  mile  so  as  to  aid  linemen  to  report  location  of  breaks 
and  repairs. 

Streams  are  crossed  by  hanging  the  wires  on  strong,  high  sup- 
ports, taking  cai*e  not  to  strain  the  wire  so  much  as  to  cause  it 
to  break. 

416.— The  description  of  Instruments  and  batteries,  their  con- 
nections and  care,  will  be  found  in  the  Manual  published  by  the 
Signal  Service  of  the  Army. 

417.— Joints.  Where  wires  have  to  be  joined  to  preserve  the 
continuity  of  the  metallic  circuit,  the  best  joint  is  the  American 
twist  joint.  To  make  this  clean  the  wires  for  a  length  of  5  or  6 
inches,  make  a  right-angle  bend  in  each  wire  about  4  inches  from 
the  end,  now  join  the  wires  so  that  the  ends  project  on  different 
sides  and  clamp  both  wires  with  a  hand  vise,  then  with  a  splicing 
iron  turn  the  ends  around  the  line  wire,  making  the  turns  as  close 
as  possible;  after  the  entire  end  is  turned  around  the  line  wire, 
cut  off  the  projecting  end  and  dip  the  joint  into  melted  solder; 
this  protects  the  joint  against  rusting.  The  details  of  this 
joint-making  are  shown  in  Figs.  7  and  8. 

418.— Military  lines  are  generally  of  the  kind  designated  as 
flying  lines — i.  e.,  they  are  intended  to  accompany  the  army  in 
the  field,  are  constructed  quickly  for  temporary  use,  and  are  as 
quickly  dismantled  and  taken  up.  The  poles  used  are  small  poles 
called  lances,  each  about  2\<2  in.  in  diameter  and  17  ft.  in  length, 
placed  2  ft.  in  the  ground,  and  run  about  40  to  the  mile.  The 
batteries,  line  lances,  and  instruments  are  carried  in  wagons 
which  accompany  the  army.  A  detailed  description  of  the  tele- 
gi'aph,  with  directions  how  to  erect  and  dismantle,  is  found  in  the 
Manual  of  Signals  for  the  U.  S.  Army.  The  ordinary  telephone 
receiver  (with  magneto  call  bell)  is  used  on  the  military  lines;  but 
for  the  use  of  outposts,  reconnoiterers  and  scouts  a  special  form 
of  telephone  cart  and  wire  has  been  adopted,  the  following  de- 
scription of  which  is  taken  from  the  Report  of  the  Chief  Signal 
Officer  of  the  Army,  1892: 

"The  frame  of  this  cart  is  constructed  of  bicycle  tubing,  and 
30  In.  bicycle  wheels  with  heavy  cushion  rubber  tires  are  used. 
The  cart  Is  fitted  with  an  automatic  spooling  device  for  reeling 


Telegraph  and  Telephone  Lmes.  189 

up  the  outpost  cable.  Tliis  device  was  made  by  F.  S.  Gahill  & 
Co.,  and  is  a  success.  The  cart  carries  5  reels  of  cable  and  1  reel 
knapsack  for  use  in  places  where  the  cart  cannot  penetrate 
owing  to  underbrush,  etc.  As  the  extreme  width  of  the  cart, 
measured  at  the  wheels,  is  only  26  in.,  it  can  follow  any  ordinary 
path  through  underbrush.  The  weight  of  the  cart  complete 
with  spooling  device,  but  without  the  reels,  is  only  53  pounds; 
when  loaded  with  reels  and  reel  knapsack,  the  total  weight 
is  157  pounds.  The  cart  is  well  balanced  upon  its  axle  by  a 
device  which  permits  the  point  of  support  to  be  changed  to  bal- 
ance the  cart  as  the  distribution  of  the  weight  is  changed  by 
the  cable  being  run  out.  In  connection  with  the  reel  cart  a  tele- 
phone kit  is  used,  and  by  attaching  the  double  connector  of  the 
kit  to  one  on  the  frame  of  the  cart  the  telephone  is  kept  in  cir- 
cuit and  conversation  can  be  kept  up  with  the  home  station. 
The  cart  with  its  load  can  be  easily  drawn  by  one  man,  and  by 
its  use  it  will  be  possible  to  connect  outposts  with  the  main 
guard,  or  brigade  with  regimental  headquarters,  or  brigade 
with  division  headquarters,  in  a  few  minutes  of  time.  The  ex- 
perience of  the  English  in  Egypt  has  proved  the  value  of  the 
field  cable  line  in  action,  as  by  means  of  these  lines  the  Com- 
manding General  was  kept  in  communication  with  different 
divisions  of  troops  and  with  those  actually  engaged  in  the  firing 
line.  It  is  proposed  to  fit  shafts  to  the  cart  so  that  a  horse  can 
be  harnessed  to  it,  thus  securing  great  rapidity  in  running  out 
the  cable.  The  cart  carries  1  2-3  miles  of  cable,  which  can  be  paid 
out  as  fast  as  a  man  moves  with  the  cart,  and  by  means  of  the 
reeling  apparatus  and  spooling  device  can  be  recovered  at  the 
rate  of  4  miles  per  hour,  or  as  rapidly  as  a  man  can  walk  with 
the  cart." 

419.— Faults  are  generally  of  three  kinds— breaks  or  discon- 
nections, leaks  or  escapes,  and  crosses  or  contacts. 

Breaks  or  disconnections  occur  when  the  metallic  circuit  is 
broken  or  cut  so  that  either  the  disconnection  is  complete,  as  when 
entirely  severed;  or  incomplete,  when  partially  cut  or  where  a  joint 
is  rnsted  so  much  as  to  increase  the  conductive  resistance.  In 
these  cases  the  instruments  will  work  weakly  or  fail  entirely. 

Leaks  or  escapes.  Where  the  insulation  is  destroyed  or  is 
defective,  of  where  a  wire  comes  in  contact  with  a  conductor  to 


190  Telegraph  and  Telephone  Lines. 

the  earth  or  with  the  earth  itself,  a  portion  of  the  current  leaks  or 
escapes.  When  the  wire  is  swinging,  the  leak  will  be  intermit- 
tent; when  constant  leakage  is  going  on,  the  instruments  will 
work  weakly;  when  the  leak  becomes  complete,  failing  altogether, 
it  is  called  "a  ground." 

A  cross  or  contact  occurs  when  two  wires,  each  carrying  cur- 
rents, are  brought  into  contact;  thus  the  instruments  on  one  line 
will  interfere  with  the  workings  of  those  on  the  other.  Generally 
occurs  from  parallel  wires  being  swung  over  one  another  by 
the  wind,  or  having  a  good  conductor  fall  so  as  to  touch  both 
wires. 

420.— Telegraph  lines  should  never  be  damaged  or  destroyed, 
except  in  obedience  to  direct  orders.  Faults  may  be  made  by 
connecting  the  wires  together  with  small  wire  (this  makes  a  bad 
cross),  or  they  may  be  connected  with  the  lightning  rods  on  the 
poles,  thus  running  them  to  the  groun<i. 

When  an  office  is  taken,  the  instruments  should  all  be  discon- 
nected and  destroyed  or  taken  away;  the  ends  of  the  wires  should 
be  tied  together.  The  batteries,  if  any,  should  be  disconnected. 
To  destroy  the  line,  cut  down  the  poles  and  burn  them  and  cut 
the  wire  into  small  lengths.  Subaqueous  lines  should  be  brought 
up  with  a  grapnel  and  a  piece  cut  out  and  cut  into  small 
pieces  and  thrown  back  into  the  water.  Subterranean  lines  are 
generally  laid  in  conduits,  and  at  regular  intervals  man-holes 
are  built  to  allow  of  repairs;  the  line  may  be  detected  by  these 
man-holes,  the  conduit  destroyed,  and  the  cables  disconnected. 


CHAPTER  XX.— Demolitions. 

421.— In  military  operations  demolitions  must  be  made  witli 
tlie  least  possible  expenditure  of  time  and  explosive.  Neverthe- 
less, a  charge  which  in  itself  seems  large  for  the  object  intended 
may  prove  economical,  in  that  it  errs  on  the  right  side  and  a  repe- 
tition of  the  work  is  not  made  necessary. 

Military  engineers,  or  troops  acting  as  such,  may  have  to  de- 
stroy bridges,  houses,  walls,  railroads,  tunnels,  stockades,  pal- 
isades, gates,  cannon,  etc.,  break  up  roads,  fell  trees  and  place 
mines.  On  account  of  their  portability,  great  destructive  effect 
and  facility  of  handling,  high  explosives  should  generally  be 
used  in  all  these  operations.  However,  where  ordinary  gun- 
poA^der  is  available,  it  may  be  used  to  advantage,  if  time  permits 
its  proper  placing  and  tamping.  Gun-cotton  is  the  standard 
explosive  for  military  work,  and  all  formulas  are  calculated  for 
its  use. 

422.— Gun-cotton,  as  made  at  the  U.  S.  Naval  Torpedo  Sta- 
tion, is  in  blocks  about  3  in.  square  and  2  in.  thick;  each  block 
is  perforated  to  allow  the  insertion  of  a  detonator,  and,  when  dry, 
weighs  about  10  oz.  When  necessary  to  use  a  «maller  amount 
than  10  oz.,  a  block  may  be  cut,  when  wet,  by  using  a  saw  or 
sharp  knife,  care  being  taken  to  place  it  between  two  boards,  so 
that  it  will  not  flake  or  crack  during  the  operation. 

Gun-cotton,  as  furnished  by  the  U.  S.  Ordnance  Department, 
is  in  small  rectangular  blocks  weighing  about  1-8  oz.  The  blocks 
contain  about  15  per  cent  of  water,  are  coated  with  varnish, 
and  can  be  shipped  or  handled  with  safety.  For  use,  a  paper 
or  cardboard  cylinder  is  made  and  the  blocks  placed  in  it.  The 
detonator  is  inserted  in  a  prepared  primer,  which  is  placed  be- 
tween the  blocks. 

Gun-cotton  will  absorb  about  30  per  cent  of  its  weight  of 
water,  and,  when  in  this  condition,  Is  comparatively  safe,  as  it 
can  only  be  ignited  by  fire  and  is  difficult  of  detonation.  When 
packed  for  transportation  the  blocks  are  placed,  while  wet,  in 
a  tin  can;  the  can  is  hermetically  sealed  or  is  left  so  that  the  water 
can  be  replaced  when  it  has  evaporated. 

When  both  are  well  tamped,  gun-cotton  has  an  explosive  force 

-13— 


PLATE  55. 


Fign-re  1. 


/•    /   y^ 


Figure  2. 

^   -------         ■  f--^ — r 


Demolitions.  193 

two  timet)  as  gieut  as  guupovvaer;  wlien  no  tamping  is  used,  it 
has  a  force  four  times  as  great. 

423.— Primers.  Wet  gun-cotton  detonates  with  much  greater 
force  than  dry,  but  it  is  necessary  that  this  action  be  set  up  by 
the  detonation  of  a  dry  primer  of  gun-cotton  placed  in  intimate 
contact  with  the  w- et  charge.  When  wet  gun-cotton  is  carried,  a 
sufficient  quantity  for  a  primer  may  be  taken  from  the  wet  case, 
placed  in  the  sun  and  allowed  to  dry;  it  is  better,  however,  in 
operations  in  the  field,  to  carr:^'  a  small  amount  of  dry  gun-cotton, 
so  as  not  to  waste  time  in  drying  the  primer. 

When  used  in  holes,  gun-cotton  should  be  dry,  as  wet  gun- 
cotton  is  difficult  to  detonate  under  such  circumstances. 

424.— Dynamite.  Dynamite  comes  in  cartridges  or  sticks 
weighing  8  oz.  each,  and  may  be  used  instead  of  gun-cotton.  It 
should  not  be  used,  however,  if  exposed  to  wet  or  if  frozen. 
Frozen  dynamite  can  be  thawed  by  placing  it  in  an  apparatus 
like  a  glue  pot,  the  dynamite  being  in  the  inner  vessel  and  the 
hot  water  in  the  outer.    It  must  not  be  thawed  at  a  fire. 

Gunpowder  may  sometimes  be  used  in  demolitions,  and  when 
so  employed  it  should  be  placed  in  stout  bags,  preferably  two,  the 
outer  one  well  tarred.  This  is  to  protect  from  accidental  explo- 
sion occasioned  by  sparks  from  the  fuse. 

425.— Explosives  should  be  placed  in  as  close  contact  as  pos- 
sible with  the  object  to  be  destroyed,  and  the  packages  compos- 
ing the  charge  should  be  in  intimate  contact  with  each  other. 

426. — Common  Detonator.  The  common  detonator  is  a  cop- 
per tube,  about  %  in.  in  diameter,  closed  at  one  end  and  partially 
filled  with  fulminate  of  mercury,  which  is  ignited  by  a  fuse. 
The  ordinary  blasting  cap  (PI.  55,  Fig.  1),  or  detonator,  is  in- 
tended for  use  with  a  fuse,  and  is  designated  as  single,  double, 
or  triple  force,  according  to  the  amount  of  fulminate  of  mercury 
used.  In  military  operations  it  is  better  to  use  the  triple- 
force  caps,  as  their  action  is  sure,  even  on  comparatively  low 
explosives.* 

427.— The  fuse  generally  used  in  this  country  to  ignite  these 
detonators  or  caps  is  that  made  by  Ensign,  Bickford  &  Co., 
Simsbury,  Conn.,  the  grade  known  as  "double-taped"  being  the 


♦Sing-le-force  caps  contain  3  grs.,  double-force  caps  6  grs.,  and  triple-force  caps 
9  grs.  of  fulminate  of  mercury. 


1^^  Demolitions. 

best  for  general  work  when  the  fuse  is  not  expcsed  to  pro- 
longed immersion  in  water  or  damp  ground.  When  it  is  nec- 
essary to  use  fuse  for  submarine  explosives,  the  water-proof 
fuse  should  be  used.  The  rate  of  burning  of  the  fuse  should 
be  found  by  experiment  before  using.  This  is  done  by  taliing 
several  pieces,  1  ft.  long,  and  finding  the  average  rate  of  burn- 
ing and  taking  this  as  the  standard.  The  rate  at  which  this  fuse 
is  intended  to  burn  is  3  ft.  per  minute,  but  it  varies  somewhat, 
so  that  when  great  nicety  is  required  it  should  be  tested  as 
above. 

428.— To  prepare  a  fuse  and  detonator  for  use,  cut  the  fuse  to  the 
length  required,  leaving  a  square  end;  insert  this  end  in  the  det- 
onator until  it  rests  against  the  fulminate,  taking  care  not  tc 
scratch  the  fulminate.  Then  crimp  the  copper  against  the  fuse  so 
as  to  hold  it  firmly:  this  is  done  by  means  of  pincers  made  for  the 
purpose;  or,  in  case  these  are  not  available,  any  pincers  or  the 
edge  of  a  dull  knife  may  be  used,  being  careful  not  to  crimp  on 
the  portion  of  the  cap  containing  the  fulminate. 

To  fire  t/un-cotton,  insert  the  detonator  in  the  hole  in  the  prim- 
ing-block, secure  it  by  tying  with  wire  or  twine,  and  when  ready, 
light  the  fuse. 

To  fire  dynamite^  a  hole  is  made  for  the  detonator  in  the  end 
of  the  cartridge  with  a  sharp  stick  or  lead  pencil  and  the  deto- 
nator, with  fuse  or  wire  attached,  is  inserted;  the  envelope  is  then 
tied  around  the  fuse,  so  that  the  detonator  cannot  become  de- 
tached from  the  cartridge,  care  being  taken  to  place  the  deto- 
nator in  the  cartridge  only  about  %  its  length,  so  that  the  charge 
may  not  be  ignited  by  sparks  from  the  fuse  before  the  detonator 
is  exploded. 

To  fire  gunpowder  (PL  57,  Fig.  5),  the  fuse  alone  is  used,  being 
placed  so  that  the  end  is  well  centered  in  the  mass  of  the  powder 
and  so  secure  that  it  cannot  pull  out. 

429.— The  simple  electric  fuse  is  so  constructed  that,  upon 
the  passage  of  a  current  of  electricity  through  a  platinum  wire  of 
sufliclent  strength  to  heat  the  wire  to  redness,  some  fleecy  gun- 
cotton  or  other  inflammable  material,  which  is  wrapped  around 
the  wire,  is  ignited.  This  fuse  may  be  used  to  fire  a  detonator  or 
to  ignite  gunpowder. 

In  PI.  55,  Fig.  2,  is  shown  a  fuse  with  a  cap,  which  cannot  be 


PLATE  56. 


FIG.l 


FIG  4, 


FIG,  6 


196  Demolitions. 

removed,  containing  a  detonating  compound;  hence  it  can  be  used 
with  best  effect  only  in  compounds  that  can  be  detonated.  It  is 
called  the  commercial  fuse  and  detonator. 

In  PI.  57,  Fig.  10,  is  shown  a  fuse  with  a  cap  containing  a  det- 
onator. The  cap  can  be  removed  and  the  fuse  used  to  ignite 
gunpowder.    It  is  called  the  service  fuse  and  detonator. 

Gun-cotton  and  gunpowder  are  fired  as  explained  in  Par.  428. 

To  fire  dynamite y  push  the  detonator  in  its  full  length  and  take 
two  half-hitches,  with  wire,  about  the  cartridges,  so  as  to  hold 
everything  in  place.    (PI.  50,  Fig.  1.) 

430.— The  Laflin  and  Rand  Exploder,  No.  3.  The  current 
of  electricity  is  generated  by  means  of  a  battery  consisting  of 
several  cells,  or  by  an  electrical  machine.  The  means  now  gen- 
erally used,  and  the  one  that  gives  surest  results,  is  the  magneto 
machine.  On  account  of  its  compactness,  portability,  and  sim- 
plicity, the  Laflin  &  Rand  Exploder,  No.  3,  is  probably  the  best 
for  all  work  where  electricity  is  to  be  the  igniting  agent.  (PI.  55, 
Fig.  3.)  The  machine  is  cased  in  wood,  and  its  dimensions  are 
13x8x5^/^  in.  It  weighs  18  lbs.  The  machine  will  fire,  under 
favorable  circumstances,  12  fuses.  In  order  that  there  may  be 
no  chance  of  failure,  a  greater  number  than  5  should  not  be  fired 
in  military  operations  by  this  machine. 

The  insulated  wire  used  to  make  connection  between  the 
machine  and  fuse  is  carried  on  a  reel.  Fig.  3.  The  connecting 
wires  between  machine  and  reel  are  attached  by  binding  posts, 
as  shown  in  the  figure. 

To  use  the  m^cMne,  reel  off  a  sufficient  amount  of  wire,  usually 
about  250  ft.,  and  connect  with  the  wires  of  the  detonator;  con- 
nect the  machine  with  the  reel,  being  careful  not  to  make  this 
connection  until  every  one  is  at  a  safe  distance  from  the  place  of 
explosion.  The  handle  on  top  of  the  box  is  now  lifted,  with- 
drawing the  ratchet  bar  to  its  full  length,  and,  when  the  time 
arrives  to  fire  the  charge,  the  bar  is  pushed  vertically  down- 
ward, moving  slowly  for  the  first  inch  or  two,  then  by  a  rapid 
but  even  pressure,  till  the  lower  end  Is  stopped  at  the  bottom  of 
the  box. 

When  more  than  one  charge  is  to  be  fired,  the  wires  leading 
to  the  several  charges  should  be  connected,  as  shown  in  PI.  57, 
Fig.  6, 


Demolitions.  197 

431.— In  all  connection  of  wires,  at  least  2  in.  of  each  wire 
must  be  cleaned  bright  and  well  wrapped  around  one  another, 
as  shown  in  PI.  55,  Fig.  4;  under  no  circumstances  simply  hook 
wires  together.  After  wires  are  joined,  the  joint  should  be  in- 
sulated by  winding  rubber  tape,  or  wide  rubber  bands,  around 
so  as  to  overlap  the  next  previous  turn.  When  water  has  to  be 
encountered,  wrap  with  rag  or  a  strip  of  linen  and  cover  with 
tar;  or,  use  rubber  tube  as  shown:  the  tube  in  this  case  is  placed 
on  one  of  the  wires,  and,  when  the  joint  is  made,  is  pulled  over  it 
and  tied  tightly  to  the  wires  on  either  side  of  the  joint.  (PI.  57, 
Fig.  9.) 

432.— To  fell  trees,  bore  a  hole  at  the  height  desired,  insert 
the  charge,  and  fire,  care  being  taken  that  the  center  of  the 
charge  is  about  the  center  of  the  tree.  If  the  charge  be  of  a 
length  equal  to  or  less  than  the  diameter  of  the  tree,  the  hole 
may  be  bored  directly  through;  but  if  greater,  then  two  or  three 
holes,  intersecting  at  the  center,  must  be  bored,  thus  putting  the 
packages  of  gun-cotton  in  intimate  contact,  and  requiring  but 
one  detonator.  The  charge  may  be  calculated  from  the  formula 
C=ys  T2,  in  which  C  is  the  charge  in  pounds  and  T  the  diameter 
in  feet. 

When  time  is  not  available  to  bore  a  hole,  a  necklace  may 
be  used.  The  charge  may  be  calculated  from  the  formula  C=3T  ^ 
in  which  C  is  the  charge  in  pounds  and  T  the  diameter  in  feet. 

Should  the  charge  be  placed  or  hung  against  the  tree,  the 
amount  as  given  by  the  formula  for  a  necklace  must  be  increased 
one-fourth. 

To  make  the  tree  fall  in  a  given  direction  a  rope  may  be  tied 
to  it,  hauled  taut,  and  secured  to  another  tree  or  strong  stake. 

The  above  method  of  felling  trees  is  more  expensive  than  with 
the  ax,  and  is  not  to  be  resorted  to  except  In  cases  of  emergency 
where  time  is  not  available  for  slower  methods.  (PI.  55,  Figs.  5, 
6,  7  and  8.) 

433.— To  destroy  bridge  timbers,  if  rectangular,  the  charge 
is  placed  across  the  whole  width  of  the  timber.  (PI.  5B,  Fig.  2.) 
The  charge  may  be  calculated  from  the  formula  C=3WT^,  In 
which  C  is  the  charge  in  pounds,  W  the  width  and  T  the  thickness 
in  feet.    If  the  timbers  are  circular  or  square,  the  formula  re- 


1^8  Demolitions. 

duces  to  C=3T«,  and  being  the  same  as  that  for  trees  where  a 
necklace  is  used,  the  charge  should  be  so  placed. 

When  high  explosives  are  not  on  hand,  the  bridge  torpedo  used 
in  the  War  of  the  Rebellion  may  be  substituted.  It  consists  of 
a  bolt  8  or  9  in.  in  length,  surrounded  by  a  tin  cylinder  2  in.  in 
diameter,  which  is  filled  with  powder.  The  ends  of  the  cylinder 
are  closed  by  iron  washers,  and  a  fuse  placed  in  one  end.  To 
use  this  torpedo,  a  hole  2^  in.  in  diameter  is  bored  in  the  timber 
and  the  torpedo  inserted,  having  its  center  at  the  center  of  the 
timber;  it  is  then  exploded  by  means  of  a  fuse.  If  necessary, 
two  may  be  placed  in  holes  bored  at  right  angles  to  each  other. 
(PI.  56.  Fig.  4.) 

434.— To  destroy  a  wooden  truss  bridge,  if  time  is  available, 
the  bridge  may  be  burned;  to  do  this,  collect  brush,  etc.,  and,  if 
possible,  place  it  under  one  end  so  as  to  bum  it  off  and  cause  the 
span  to  drop,  but  if  not  possible,  build  the  fire  in  the  center  of  the 
span;  it  will  burn  through  and  cause  rupture  in  the  center.  If  time 
is  not  available,  blow  away  the  main  brace  of  the  panel  nearest 
to  an  abutment  or  pier;  it  is  really  necessary  to  blow  only  one  side 
down,  but  it  is  better  to  be  sure  and  destroy  both  sides.  If  the 
bridge  has  an  arch  of  wood  besides  the  truss,  then  destroy  the 
arch  on  each  side.  It  is  better  to  attack  the  span  over  the  deepest 
water. 

435.— Palisades  may  be  cut  down  with  axes  or  saws,  the  cuts 
being  made  near  the  bottom:  ropes  are  attached  to  the  tops  of 
the  timbers  to  assist  in  bringing  them  down;  or  the  earth  at  the 
bottom  may  be  dug  out  and  the  palisade  pulled  over. 

Palisades,  up  to  10  in.  in  thickness,  may  be  blown  down,  when 
the  timbers  are  close  together,  with  4  lbs.  of  gun-cotton  per  run 
ning  foot. 

436.— Stockades  may  be  cut  down  with  axes  or  saws,  as  ex- 
plained for  palisades. 

They  may  be  blown  down  with  4  lbs.  of  gun-cotton  per  run- 
ning foot. 

If  the  timbers  are  squared,  the  blocks  of  cotton  may  be  fas- 
tened to  a  thin  board  and  placed  against  the  foot  of  the  stockade; 
but  if  of  rough  logs,  tie  the  blocks  together  so  that  they  may 
adapt  themselves  to  the  form  of  the  timbers. 

When  stockades  are  double,  and  separated  by  a  distance  of 


Demolitions.  199 

one  yard--25  lbs.  of  gun-cotton  per  running  foot  or  one  charge  of 
80  lbs.  may  be  placed. 

Railway-iron  stockades  are  breached  by  7  lbs.  per  running 
foot. 

In  all  cases,  distribute  the  charge  so  as  to  cover  the  length 
desired  to  be  breached. 

437.— Gates  may  be  blown  in  with  50  lbs.  of  gun-cotton  ex- 
ploded in  one  charge.  The  charge  is  hung  against  the  center  of 
gate  by  means  of  a  sharpened  pick  or  on  a  nail.  This  charge  is 
large,  but  gates  will  generally  be  strengthened  in  some  manner 
on  the  inside.  (PI.  57,  Fig.  4.)  The  gates  of  Pekin  were  opened 
by  a  couple  of  shots  from  3.2-inch  field  guns  directed  at  the  locks. 

438.— Houses  may  be  blown  down  or  shattered  by  placing 
charges  in  the  center  of  the  floor  and  closing  all  outlets,  such  as 
doors,  windows,  etc.  Charge  according  to  the  size,  20  lbs.  being 
sufficient  for  small  houses. 

439.— Walls.  The  charge  should  be  placed  against  the  bot- 
tom, close  to  the  wall,  and,  if  possible,  should  be  tamped.  If 
time  permits,  a  channel  may  be  cut  in  the  wall  at  the  seat  of  the 
charge.  The  charge  untamped  may  be  computed  from  the  for- 
mula C=%WT  2  in  which  C  is  the  charge  in  pounds,  W  the  width 
of  wall  to  be  breached,  and  T  the  thickness;  W  and  T  are  in  feet. 
When  tamped  with  earth  equal  to  the  thickness  of  the  wall,  half 
the  above  charge  may  be  used.    (PI.  57,  Fig.  2.) 

440.— Masonry  bridge  piers  may  be  destroyed  by  a  charge 
calculated  from  the  formula  0=  W  T  ^ ,  C,  W,  and  T  being  the 
same  as  in  par.  439.  In  order  to  avoid  using  so  much  gun-cotton, 
it  is  better  to  place  small  charges  in  chambers  excavated  as  deep 
as  possible  in  the  masonry,  and  explode  all  simultaneously;  cal- 
culate charges  as  for  walls. 

441.— A  masonry  bridge  arch  may  be  destroyed  by  attacking 
the  haunches  or  the  crown.  The  haunches  are  the  best  points  of 
attack,  two  trenches  being  dug  across  the  width  of  the  roadway 
down  to  the  back  of  the  arch.  If  this  is  not  possible,  attack 
the  crown.  A  single  trench  across  the  width  of  the  roadway 
may  be  used,  but  it  is  better  to  use  two,  each  placed  from  the 
crown  a  distance  equal  to  one-half  the  width  to  be  breached.  The 
charge  untamped  may  be  calculated  from  the  formula  0=%WT2, 
in  which  C,  W,  and  T  are  the  same  as  in  par.  439.  When  the 
charge  is  tamped  with  a  depth  of  earth  equal  to  the  thickness  of 


200  Demolitions. 

the  arch,  one-half  the  amount  given  by  the  formula  is  used.  (PI. 
57,  Fig.  3.) 

442.— Tunnels  may  be  destroyed  by  placing  charges  back  of 
the  masonry  at  the  spring  of  the  arch.  If  possible,  the  charge 
should  be  placed  in  a  chamber  excavated  behind  the  arch  and 
well  tamped.  Tunnels  should  be  blown  in  at  several  places,  so 
as  to  render  It  impossible  to  repair  them  in  a  short  time.  Charges 
as  for  bridge  arches.    (PI.  57,  Fig.  8.) 

443.— To  cut  steel  rails,  use  one  block  of  gun-cotton,  weight 
8  ozs.,  tie  the  block  against  the  web  of  the  rail  with  wire  or  twine, 
and,  if  possible,  tamp  well  with  earth,  and  explode.  (PI.  56, 
Fig.  8.) 

To  blow  a  piece  of  some  length  out  of  a  rail,  arrange  two 
charges  of  8  ozs.  as  shown  in  Fig.  5,  placing  one  on  each  side  of 
the  rail  at  a  distance  apart  of  5  or  6  ft.;  these  should  be  exploded 
by  use  of  a  magneto  machine,  so  that  the  action  may  be  simul- 
taneous in  both  charges;  the  section  will  be  blown  out  and  turned 
on  its  center,  making  a  large  opening. 

444.— Switch  points  may  be  destroyed  by  lodging  8  ozs.  of  gun- 
cotton  between  the  outer  rail  and  the  pivot  end  of  the  switch 
point,  being  careful  to  tamp  as  completely  as  possible.  ("A,"  PI. 
51,  Fig.  11.)  In  the  case  of  frogs,  8  ozs.  placed  in  the  angle  of  the 
frog  will  destroy  the  point  and  render  it  useless.  ("A,"  PI.  52, 
Fig.  1.) 

A  great  length  of  railway  may  be  disabled  at  a  very  rapid 
rate  by  making  use  of  hand-cars  loaded  with  gun-cotton,  pre- 
pared lengths  of  fuse  inserted  into  detonators,  torches,  and 
copper  wire  for  binding  the  gun-cotton  to  the  rail.  One  non- 
commissioned officer  and  seven  men  will  be  necessary;  two  run 
the  hand-car:  two  sit  on  the  hand-car  and  fix  the  detonators  to 
the  gun-cotton,  prepare  binding  wire  and  hand  out  the  charges: 
two  men  receive  the  charges  and  bind  them  to  the  rails;  two 
follow  at  about  150  yards  In  rear  and  fire  the  charges  as  they 
pass. 

445.— To  cut  wrought-iron  plates,  the  charge  is  found  from 
the  formula  C=1.5Wt^,  in  which  C  is  the  charge  in  pounds,  W  the 
width  in  feet,  and  the  thickness  in  inches.  The  charge  should 
be  placed  entirely  across  the  plate  to  be  cut. 

446.— To  cut  an  iron  bridge  beam  or  girder  (PI.  56,  Figs.  6 


Demolitions.  201 

and  7),  calculate  the  charge  for  each  separate  cross-section  to 
be  cut,  using  the  formula  in  par.  445,  and  add  the  results;  the 
sum  will  be  the  charge  required.  The  charge  is  most  conven- 
iently placed  on  the  side  of  the  beam,  reaching  entirely  across 
and  bound  on  with  wire,  the  primer  being  in  the  center  of  the 
charge.  If  possible,  a  board  should  be  tied  over  the  charge  and 
earth  tamped  around  it.  When  time  is  not  available  for  placing 
the  charge  as  above  described,  it  may  be  laid  on  top  of  the  beam 
or  on  the  flange. 

447.— Girder  bridges  not  longer  than  20  ft.  may  be  overturned 
by  levers  and  thrown  off  the  abutments.  When  this  cannot  be 
done,  the  gun-cotton  charge  may  be  calculated  and  placed  as  de- 
scribed for  iron  girders. 

448.— In  iron  truss  bridges  the  most  favorable  place  for  the 
charge  is  at  the  center  of  the  span  on  the  lower  chord.  When 
the  bridge  is  of  the  variety  known  as  a  deck  bridge,  the  charge 
should  be  placed  on  the  top  member.  When  the  lower  or  ten- 
sion member  is  composed  of  eye-bars,  the  charge  should  be  placed 
between  alternate  pairs  of  eye-bars  as  near  to  the  coupling- 
pin  as  possible.  The  charge  may  be  calculated  as  in  par.  446. 
(PI.  57,  Fig.  1.) 

449.— When  bridges  are  supported  by  iron  or  wood  piers,  it  is 
sometimes  possible  to  destroy  the  piers,  and  thus  bring  down  the 
entire  structure.  In  attacking  a  pier,  it  is  best  to  blow  out  the 
supports  on  both  sides,  as  this  will  bring  down  all  of  the  bridge 
resting  on  the  pier.  The  charges  may  be  calculated,  if  of  stone, 
by  par.  440;  if  of  iron,  by  par.  445. 

450.— In  destroying  suspension  bridges,  blow  down  the  tow- 
ers below  the  saddles,  excavate  and  blow  out  one  of  the  an- 
chorages, or  cut  the  cable  with  gun-cotton.  The  charge  for 
bridge  cables  is  calculated  as  for  cutting  iron  plates;  the  charge 
must  be  carefully  placed,  so  as  to  be  in  close  contact  with  the 
cable.  If  the  cables  are  made  of  plates,  the  plates  may  be  cut 
with  .2:un-cotton,  as  in  the  case  of  eye-bars  cited  above. 

451.— Field  and  siege  guns  may  be  disabled  by  detonating 
1%  pounds  of  gun-cotton  on  the  outside  near  the  muzzle.  For 
heavier  fortress  guns,  detonate  4  pounds  in  the  bottom  of  the 
bore,  tamping  with  sand.  Tbe  carriages  may  be  destroyed  by 
using  gun-cotton, 


PLATE  57. 


iFIG.l. 


FIG.  2. 


FIG.  4 


FIG.3. 


FIG  6, 


r  IG  10.      ^  •  Service  Fuye 


„    bridia 
f.    prinrlna 
h    fulTTtinqre  cf  mercury, 
lo  to  ^4 grains.    ^ 

drop 

chwoocL. 


Z  paper,  discs  Xeld  by 
2.  7  ^  ^oUocTipn  / 
K.  plug  cf  beechwoot 


PIG.  9. 


Demolitions.  203 

452.— Approximate  Relative  Strength  of  Some  of  the  High 
Explosives. 

Explosive  gelatine 128.3 

Nitro-glycerine 120.3 

Gun-cotton 100. 

Dynamite,  No  1,  75  per  cent  Nitro-glycerine 97.8 

Rack-a-rock 74.2 

Dynamite,  50  per  cent 72.7 

453.— Destruction  of  Obstacles.  Wire  entanglements  may 
be  destroyed  by  cutting  with  wire  nippers,  or,  if  they  are  not  at 
hand,  then  the  ordinary  hand-ax  will  do,  taking  care  to  cut  against 
tlie  picket. 

Abatis  is  very  difficult  to  destroy  and  cannot  be  removed 
while  fire  can  be  brought  to  bear  on  the  spot.  Pry  up  the  pick- 
ets with  levers  and  attach  ropes  to  the  butts  of  trees  and  haul 
away. 

Small  pickets  are  cut  through  with  the  ax,  or,  if  possible, 
pulled  up. 

Small  pits  are  filled  with  earth,  brush,  or  covered  by  planks, 
fascines,  or  bales  of  hay. 

Automatic  torpedoes  are  easily  destroyed  by  driving  animals 
up  and  down  the  line  suspected  of  containing  them. 

454. — The  following  table  gives  in  a  concise  form  all  Inlrorma- 
tion  necessary  for  the  use  of  gun-cotton  and  gunpowder.  The 
table  shows  approximately  the  value  of  the  different  high  explo- 
sives as  compared  with  gun-cotton. 

NOTE.— Charges  are  in  lbs.;  W  and  T  are  in  feet;  t  is  in  inches. 

W  is  width  of  breach  to  be  made;  T  or  t  is  thickness  of  object 
to  be  demolished. 

Gunpowder  is  assumed  to  be  roughly  tamped  with  sand-bags. 
Gun-cotton  is  untamped.  If  the  gun-cotton  is  tamped,  the  charges 
may  be  reduced  by  about  one-half. 

Charge  of  gun-cotton  must  be  equal  in  length  to  the  breach 
which  Is  to  be  made. 


204 


Easty  Demolitions. 


Object  Attacked. 

Gunpowder 

Gun-cotton 

Remarks. 

Brick  arch ^ 

I 

IWT2 

2  lbs.  per 

foot  run 

iWT2 
|WT2 

The   length   of 

bleach,    W,  should 

►  not  be  less  than  the 

height  of  the  wall 

to  be  brought  down. 

Brick  wall,  2  ft.  or 
less 

Brick  wall  over  2  ft. 
thick 

Brick  piers 

Hard  wood  {e.  g.y  oak, 

40  to  100 

3WT2 

In    a    concentrated 

elm),  in   any  form, 

lbs.    for 

charge,   or   for    trees 

whether      stock- 

stockade 

not  over  12  in.  diame- 

ade, palisade,  sin- 

ter, in  a  necklace. 

gle  timbers,    trees, 

|T2 

In  auger-hole,  when 

etc. 

the  timber  is  not  per- 
fectly round,  T  =  the 
smaller  axis. 

Soft  wood 

Half  the 

charges 
wood. 

for  hard 

Breastwork    of    hori- 

60 to    80 

4  lbs.  per 

zontal    balks,     or 

lbs.   per 

foot. 

earth  between 

5  ft. 

sleepers  up  to  3  ft. 

6  in.  thick 

7  lbs.  per 

Heavy  rail  stockade. 

foot. 

Fortress  gate 

200  lbs. 

50  lbs. 

Iron  plate 

#Wt2 

In  this  case  only^  t 
is  in  inches. 

2  •»  •• 

Kield  or  siec^e  cnins 

\h  lbs. 

On  chase  near  muz- 

A      J.V«XV&     V^X      \3X.\^^^\^     ^L  ULXAv?     •     • 

zle. 

Heavier  guns 

4  lbs. 

In  bottom  of  bore, 
tamped  with  water  or 

sand. 

First-class  iron  rail . . 

10  ozs. 

Touching     web    of 
rail  and  near  a  chair. 

First-class  steel  rail . . 

8ozs. 

Four    rails    placed 
round  the  charge  will 

be  cut  simultaneously 

by  it. 

CHAPTER  XXI.— Camping   Expedients. 

455.— There  are  a  few  general  principles  wliich  should  be  ob- 
served in  selecting  a  camp,  whether  the  troops  are  to  be  estab- 
lished in  bivouac,  in  tents  or  in  huts.  These  principles  relate  to 
the  health  and  comfort  of  the  troops,  the  facilities  for  communi- 
cation, the  convenience  of  wood  and  water,  and  the  resources  of 
the  locality  in  provisions  and  forage. 

456.— For  an  intrenched  camp  the  ground  must  be  selected 
with  particular  reference  to  its  adaptability  for  defense  and  the 
camp  arranged  with  that  object  in  view,  at  the  same  time  observ- 
ing as  many  of  the  other  requirements  as  possible. 

457.— Dry  and  healthy  sites,  dependent  on  soil:  Grardte, 
metamorpMc  and  trap  rocks,  usually;  clay  slates,  but  drinking  wa- 
ter is  scarce;  limestone  generally,  but  the  water  is  hard,  clear 
and  sparkling,  though  sonletimes  contaminated;  deep  permeable 
sandstones,  if  the  air  and  soil  are  dry;  deep  gravels,  unless  lower 
than  surrounding  country;  pure  sand,  deep  and  free  from  organic 
matter;  well-cultivated  soils  generally;  gravelly  Mllocks,  the  very 
best. 

458.— Unhealthy  sites,  dependent  on  soil:  Magnesium  lime- 
stone; shallow  sandstone  underlaid  with  clay;  clay  amd  alluvial 
soils  generally;  rice  fields;  made  soils  usually;  newVy  plowed 
ground. 

459.— Healthy  sites,  independent  of  soil:  The  hest  is  on  a 
divide  or  saddle,  unless  too  much  exposed  or  without  water.  The 
next  best  is  near  the  top  of  a  slope,  and  the  southern  side  is  prefera- 
ble Jo  the  northern;  banks  of  running  rivers  are  good,  if  not 
marshy. 

460.— Unhealthy  sites,  independent  of  soil:  Enclosed  valleys, 
ravines,  or  the  mouths  of  long  ravines,  ill-drained  ground,  the  neigh- 
borhood  of  marshes,  especially  if  the  wind  blows  from  them.  If 
forced  to  camp  near  a  marsh,  the  windward  side  should  be  select- 
ed, and,  if  possible,  have  a  hill  or  a  screen  of  woods  or  brush  be- 
tween the  camp  and  marsh.  Moss  generally  indicates  marshy 
ground. 

461.— Sites  affected  by  surrounding  vegetation:  Herbage, 
or  closely  lying  grass,  is  always  healthy,  but  should  be  kept 


206  Camping  Expedients. 

cut  and  all  weeds  destroyed;  heavy  brush  about  a  marsh  should 
not  be  removed.  Trees,  in  cold  countries,  break  the  winds; 
in  hot  countries  they  cool  the  ground  and  raay  protect  against 
malarial  currents;  so  should  only  be  removed  with  judgment. 

462.— In  selecting  camps,  wood,  water,  and  grass  should  be 
secured,  if  possible,  together  with  good  drainage,  but  marshy 
ground*  should  not  be  occupied  even  for  a  night. 

Old  camp-grounds  should  never  be  occupied,  if  avoidable; 
instead,  go  as  far  as  possible  to  the  windward  side  of  them. 

The  site  having  been  selected,  the  details  of  castrametation, 
or  the  laying  out  of  camps  for  the  different  arms,  will  be  found  in 
the  authorized  Drill  Regulations  of  each. 

463.— Water  is  more  immediately  necessary  to  life  than 
food. 

Each  man  requires,  in  bivouac  on  the  march,  for  drinking  and 
cooking  3  to  4  quarts  per  day,  and  am  equal  amount  for  washing. 
In  camps,  5  gallons  per  day  for  all  purposes. 

Hospitals  require  several  times  as  much  per  man  per  day. 

Horses,  mules,  and  cattle  require  from  G  to  10  gallons  each 
per  day  for  drinking.  It  should  be  soft  and  clean,  if  possible. 
Sheep  and  hogs  require  from  2  to  4  quarts  each  per  day. 

464.—/^  is  imperative  J  on  going  into  camp,  tJiat  the  supply  he  imme- 
diately looked  after  and  a  guard  placed  over  it.  If  the  supply  be 
small,  special  precautions  must  be  taken  and  an  officer  put  in 
charge. 

465.— Good  drinking  water  should  be  bright,  colorless,  odor- 
less, free  from  sediment,  of  pleasant  and  sparkling  taste. 

Rain  water,  collected  from  a  clean  surface,  after  the  atmos- 
phere has  been  well  washed,  is  the  purest  in  nature.  Springs 
whose  origins  are  remote  from  habitations,  streams  flowing 
through  uninhabited  regions,  and  large  lakes,  furnish  the  next 
best  sources  of  supply. 

466.-7/"  the  supply  be  from  a  lake,  pond,  or  stream,  separate 
places  for  obtaining  water  for  men  and  animals  must  be  marked 
out,  and  care  taken  that  the  margin  is  not  trampled  into  mud  and 
the  water  made  turbid.  Where  this  is  likely  to  occur  when  ani- 
mals are  watered  direct  from  the  source  of  supply,  a  hard  bottom 
should  be  formed  foy  them  to  stand  on,  and  a  barrier  formed  to 
prevent  them  going  out  too  far. 


Camping  Ewped/ients.  207 

It  is  better,  wliea  couveuieut,  to  arrange  rows  of  sunken  half- 
barrels,  or  board  trouglis  raised  above  tlie  ground,  into  wMch  the 
water  can  be  drawn.  If  the  supply  be  limited,  it  may  be  neces- 
sary to  connect  the  troughs  to  prevent  waste;  if  not  limited,  each 
should  be  supplied  direct  from  the  source  and  the  overflow 
drained  off.  Even  when  drinking  from  a  running  stream,  the 
animals  below  get  foul  water.  To  prevent  the  ground  around  the 
troughs  becoming  muddy,  it  should  be  paved  and  drained  along 
the  whole  length  and  for  a  distance  of  10  or  12  ft.  back.  Where 
troughs  cannot  be  constructed,  trenches  lined  with  puddled  clay 
may  be  made  to  answer. 

Arrangements  should  be  made  so  animals  may  be  brought  up 
from  one  direction  and  leave  in  another  without  confusion  or 
crowding. 

467.—//  iJie  supply  be  from  a  stream,  the  water  for  drinking 
and  cooking  for  the  troops  is  drawn  highest  up;  for  the  animals 
to  drink,  next  below;  and  for  washing,  bathing,  etc.,  lowest  down; 
while  all  drainage  should  enter  below  where  any  water  is 
taken. 

If  the  stream  be  small,  it  may  be  necessary  to  construct  a 
series  of  small  reservoirs  by  building  small  dams  across.  Ani- 
mals drink  better  and  more  rapidly  where  water  is  5  or  6  in. 
deep. 

468.— If  unavoidable,  water  from  small  ponds  and  shallow 
wells  should  only  be  used  after  being  boiled  half  an  hour,  then 
aerated  and  filtered.  In  fact,  the  only  safe  method  of  treating  any 
water  that  is  not  known  to  be  pure  is  to  boil  it  thoroughly  for  at 
least  half  an  hour,  or  distil  it,  one  or  the  other  of  which  methods 
should  always  be  insisted  upon. 

469.—//  the  supply  be  fro7n  springs,  each  should  be  enlarged 
and  surrounded  by  a  low  puddled  wall,  to  keep  out  surface  drain- 
age. They  may  be  lined  with  casks  or  barrels  charred  inside,  or 
gabions,  afterwards  working  in  puddled  clay  between  the  earth 
and  linings.  The  overflow  may  be  received  into  a  succession  of 
casks  let  into  the  ground  close  together. 

Surface  springs  should  be  sought  for  in  hollows,  at  the  foot 
of  hills,  w^here  the  earth  is  moist,  the  grass  unusually  green,  or 
the  thickest  mists  arise  mornings  and  evenings. 

470.— If  water  is  not  immediately  available,  it  may  be  neces- 

-14- 


208  Camping  Expedients. 

sary  to  dig  wells.  The  most  expeditious  means  of  doing  so  is  to 
use  Well  Augers.    (PI.  58,  Figs.  1,  2,  and  3.) 

471.— To  dig  a  well,  an  auger  is  attaclied  to  a  rod  suspended 
from  a  rope  passing  over  a  pulley  at  the  top  of  a  derrick  or  tripod 
and  thence  to  a  windlass.  To  the  auger  rod  is  secured  an  arm  or 
arms,  by  which  the  auger  is  turned  by  hand  and  so  screwed  down 
into  the  earth.  About  eight  turns  till  the  auger,  which  is  then 
lifted,  emptied  and  replaced. 

472.— r/te  auger  for  hoiiiiij  in  quicksand  (Fig.  3)  is  shaped  simi- 
larly to  the  ordinary  wood-boring  auger,  but  with  a  hollow  shank, 
so  that,  when  lifted,  no  suction  is  produced.  When  the  thread  be- 
comes loaded,  the  auger  is  drawn  up  into  an  enclosing  cylinder, 
removed  from  well  and  emptied. 

473.— Driven  wells.  The  driven  tube-well  consists  of  a  tube 
about  3  ft.  long,  perforated  with  holes,  and  furnished  with  a  steel 
point  of  bulbous  form  (Fig.  4)  and  as  many  other  plain  iron  tubes 
as  may  be  necessary. 

The  form  of  the  point  serves  to  clear  a  passage  for  the  sockets 
by  w^hich  the  tubes  are  screwed  together. 

474.— To  drive  a  well,  a  tube  is  screwed  to  the  point  (Fig.  5) 
and  on  this  a  clamp  is  fastened  by  two  bolts  at  about  3  ft.  from 
the  lower  extremity  of  the  point.  Next,  an  iron  driving  weight, 
or  monkey,  is  slipped  on  the  tube  above  the  clamp.  The  tube  thus 
furnished  is  raised  and  held  vertically  in  the  center  of  a  guide, 
in  which  it  is  retained  by  a  latch.  The  w^hole  being  now  arranged 
in  position,  ropes  are  made  fast  to  the  monkey  and  passed  over 
pulleys  on  the  guide,  and  driving  commenced  by  two  men  pull- 
ing the  ropes  and  allowing  the  monkey  to  fall  on  the  clamp.  As 
soon  as  the  clamp  reaches  the  ground,  the  monkey  is  raised  and 
held  up,  the  clamp  loosened  and  raised  1.5  or  2  ft.,  tightened, 
and  the  driving  continued  as  before  until  the  top  of  the  tube 
comes  below  the  hole  in  the  top  of  the  guide  head,  when  the 
lengthening  bar  (Fig.  7)  is  dropped  into  the  top  of  the  well-tube. 
The  lengthening  bar  consists  of  a  length  of  the  well-tubing  with 
a  smaller  pipe  brazed  into  one  end  and  projecting  about  1  ft., 
which  fits  into  the  well-tube.  This  bar  keeps  the  tube  steady 
and  serves  as  a  guide  for  the  monkey  to  slide  on  until  the  top 
of  the  well-tube  reaches  to  within  a  foot  of  the  ground.  The 
lengthening  bar  is  then  removed,  another  tube  is  screwed  on, 


PLATE  58. 


Pig.l 


Fig.  2. 


Fig.3. 


Fig.l3. 


J^Ll 


210  Campi/ng  Expedients. 

and  the  driving  continued  until  water  is  reached.  A  hollow 
iron  plumb  is  frequently  lowered  into  the  tube  to  ascertain  when 
water  has  been  reached  or  whether  earth  of  any  kind  has  got 
into  it. 

Accumulations  in  the  tube,  of  a  loose  sandy  nature,  can  be 
pumped  up,  by  screwing  a  funnel  (Fig.  8)  on  top  of  the  tube,  then 
lowering  into  it  through  the  funnel  a  small  tube  with  a  pump 
attached.  Water  poured  into  the  funnel  runs  down  outside  the 
smaller  tube  and  is  pumped  up  through  it,  bringing  the  mud  and 
sand.  When  water  is  struck,  and  stands  several  feet  in  the  tube, 
the  pump  is  screwed  on  to  the  well-tube. 

The  well  can  also  be  driven  without  the  use  of  the  tripod  sup- 
ports (Fig.  6),  care  being  taken  to  keep  the  tube  vertical  by  means 
of  guy-ropes.  Such  a  well  can  be  driven  from  10  to  20  ft.  per  hour. 
The  tubes  can  be  withdrawn  without  damage  by  reversing  the 
operations  of  driving.    (Fig.  9.) 

475.— The  tube-well  is  not  intended  for  piercing  rock,  or 
solid  stone  formations,  but  is  quite  capable  of  penetrating  very 
hard  and  compact  soils.  When  striking  rock,  stone,  or  deep  beds 
of  clay,  it  is  best  to  pull  up  the  tube  and  try  in  another  spot,  for 
by  going  a  little  distance  off  water  will  in  many  cases  be  found. 

476.— Clarification  of  water.  Water  usually  contains  min- 
eral and  organic  substances  in  solution  and  in  suspension.  ^Sub- 
stances in  solution  completely  disappear  and  cannot  be  entirely 
filtered  out.  Substances  in  suspension  do  not  entirely  disappear 
and  may  be  filtered  out. 

477.— Hard  water  contains  one  or  more  substances,  as  lime,  mag- 
nesia, iron  and  others,  in  solution,  which  are  liable  to  produce 
intestinal  troubles  to  persons  unaccustomed  to  them.  Cooking 
vegetables  in  it  is  very  difficult.  Washing  with  it  requires  a 
great  deal  of  soap. 

The  hardness  of  water  may  be  partially  removed  by  boiling 
for  half  an  hour  or  so,  or  by  adding  a  small  quantity  of  wash- 
ing soda,  or  by  adding  a  couple  of  ounces  of  quicklime  to  100 
gallons. 

478.— Substances  in  suspension  may  be  largely  removed  hy  pre- 
cipitation and  filtration. 

479.— Precipitation  is  allowing  such  matter  as  will  to  settle 
through  Its  greater  specific  gravity,  or  by  inducing  it  to  do  so 


Ca/mping  Expedients.  211 

through  some  harmless  chemical  or  mechanical  action.  For 
which  purpose  may  be  used  about  6  grains  of  crystallized  alum 
to  the  gallon,  or  tannin  in  small  quantities,  and  letting  stand  sev- 
eral hours  before  using;  bruised  cactus  leaves,  also  tea  leaves 
that  have  been  used,  act  similarly;  citric  acid,  1  oz.  to  16  gal.,  or 
borax  and  alum,  1-3  oz.  each,  or  1  to  2  tablespoonfuls  of  ground 
mustard  to  a  barrel,  improves  water. 

480.— Piltration  is  mechanically  arresting  and  attracting  sus- 
pended matter,  and  removing  dissolved  matter  in  the  water.  Fil- 
tering materials  act  only  for  a  short  period  and  should  be  fre- 
quently cleaned. 

4:81, ^Materials  which  may  he  used  are  sponge,  wool,  and  like 
articles  for  straining,  but  must  be  constantly  removed  and 
cleaned.  Clean  sand,  gravel,  and  porous  stone  remove  sus- 
pended matter,  but  have  little  or  no  effect  on  dissolved  organic 
matter.  Iron  sponge,  a  compound  of  sawdust  and  iron  oxide 
heated  in  a  furnace,  and  Garferal,  sl  composition  of  charcoal,  iron, 
and  clay,  are  efficient  for  removing  mineral  matter.  Bone-black 
or  animal  charcoal,  and  wood  charcoal,  when  freshly  burned,  ab- 
sorb mineral  matter  for  a  couple  of  weeks,  but  their  chief  action 
is  on  organic  matter. 

482.— Charcoal  may  be  made  by  digging  in  the  ground  a  cir- 
cular pit,  some  6  in.  deep  by  4  or  5  ft.  across,  then  placing  a  large 
pole  or  bundle  of  brushwood  vertically  in  the  center.  Around 
this  the  wood  to  be  burned  is  piled,  forming  a  kind  of  cone.  The 
pile  is  then  covered  with  brush,  and  on  this  a  layer  of  4  or  5  in.  of 
earth.  (Fig.  10.)  The  center  pole  is  then  removed  and  a  fire 
lighted  in  its  place,  receiving  air  from  vents  left  at  the  bottom  for 
that  purpose.  The  fire  proceeds  from  the  center  outwards,  and, 
if  burning  properly,  the  smoke  is  thick  and  white.  If  it  does 
not  spread  to  every  part,  new  vents  must  be  made.  If  the  smoke 
becomes  thin  and  a  blue  flame  appears,  it  is  burning  too  fast,  and 
vents  must  be  stopped  up  or  more  earfh  thrown  on.  When  the 
smoke  ceases  to  escsne,  the  vents  and  chimney  are  closed  and  the 
pile  allowed  to  stand  for  a  couple  of  days  until  it  cools. 

From  20  to  25  per  cent  of  charcoal  is  thus  obtained. 

483.— A  convenient  portable  filter  (Fig.  11)  is  made  by 
taking  a  small  cylinder  of  compressed  carbon  and  inserting  it 
In  9,  rubber  tube  in  such  a  manner  that  the  carbon  end  may 


212  Camping  Expedients. 

be  immersed  in  the  water,  then  applying  the  mouth  to  a  mouth- 
piece at  the  other  end  of  the  tube,  and  drawing  the  water  through. 

484.— The  Success  Filter  (Fig.  12)  consists  of  a  cylindrical 
porous  stone  4  in.  long  by  4  in.  in  diameter  with  a  hole  bored  in 
one  end.  In  this  is  fitted  a  rubber  gasket,  through  which  passes 
an  iron  tube  that  is  fastened  into  the  bottom  of  a  barrel,  jar,  or 
bucket.  The  water  filters  through  the  stone  into  the  hole  inside 
and  passes  out  through  the  tube  into  a  receiving  vessel  below. 
(Fig.  13.) 

By  fastening  the  iron  tube  into  the  bottom  of  a  large  empty 
tomato  or  peach  can,  in  which  the  stone  is  placed  on  the  tube  and 
wedged  fast,  then  fastening  a  rubber  tube  2  or  3  ft.  long  on  the 
iron  tube  outside  of  the  can,  a  syphon  filter  is  obtained.  The 
action  is  set  up  by  exhausting  the  air  from  the  stone,  after  the 
can  and  stone  are  immersed  in  water,  by  sucking  on  the  end  of  the 
rubber  tube  until  the  water  is  started. 

485.— A  simple  water  filter  may  be  made  by  stuflSng  a 
piece  of  sponge  in  a  hole  in  the  bottom  of  a  cask,  flower  pot,  or 
other  vessel  (Fig.  14),  then  placing  above  this  a  layer  of  coarse 
sand,  then  a  layer  of  pounded  charcoal  3  or  4  in.  thick,  then 
another  layer  of  coarse  sand  and  on  this  a  layer  of  coarse  gravel. 
The  layers  should  be  thick  as  possible,  and  tightly  compressed, 
and  washed  thoroughly  clean  before  being  used.  The  differ- 
ent layers  may  be  prevented  from  mixing  by  perforated  boards, 
or  otherwise.    Another  form  may  be  made  as  shown  in  Fig.  15. 

486.— Casks,  or  barrels,  charred  on  the  inside  (and  occasionally 
cleaned,  brushed,  and  recharred),  improve  water. 

487.— Latrines.  Arriving  on  the  site  of  a  camp,  one  of  the 
first  duties  is  to  designate  the  places  to  attend  to  the  calls  of  na- 
tiire,  and  there  dig  latrines.  Urinals  should  be  placed  nearer  the 
camp  and  of  easy  access. 

The  only  exception  to  digging  latrines  Is  when  the  command 
is  very  small,  is  certain  to  march  the  next  day,  and  no  other 
troops  are  to  follow. 

488.— Latrines  and  urinals  should  be  so  placed  as  not  to  be  in 
the  course  of  the  prevailing  winds  to  the  camp,  and  must  be  so 
situated  that  they  cannot  pollute  the  watpr,  either  directly  or  by 
iRoakage. 


Camping  Expedients.  213 

489.— A  small,  shallow  trench  will  suflSce  for  a  single  night, 
and  should  invariably  be  filled  in  the  morning  before  marching. 

For  longer  periods,  a  trench  2  or  3  ft.  wide  at  top,  from  2  to  10 
ft.  deep,  and  12  to  15  ft.  long  for  every  100  men,  should  be  dug, 
throwing  the  earth  to  the  rear,  from  which  a  layer  of  a  few  inches 
should  be  thrown  into  the  trench  every  day,  or  oftener  if  neces- 
sary. Lime  or  charcoal  may  also  be  used  to  deodorize  the 
soil. 

It  is  better  to  increase  the  number  of  trenches  than  to  make 
any  one  trench  too  long. 

Shallow  latrines  should  be  discarded  when  filled  within  a  foot 
of  the  surface,  and  completely  filled  in  with  earth;  deep  ones  when 
within  3  or  4  ft.  of  the  surface. 

All  latrines  should  be  filled  in  and  marked  before  marching. 

490.— In  temporary  camps,  latrines  may  be  provided  with  seats 
of  a  pole  and  a  back,  and  be  screened  by  bushes,  canvas,  or  other 
means.    (Fig.  16.) 

491.— Kitchens.  On  going  into  camp,  kitchens  should  be 
promptly  established,  and  in  the  same  relative  positions  as  if  the 
camp  were  going  to  last  a  month  or  more.  A  pit  should  be  dug 
near  by  for  strictly  liquid  refuse,  while  solid  matter  should  be 
placed  in  a  box  or  barrel  for  the  police  party  to  remove. 

4:92.— When  fuel  is  plentiful,  a  trench  of  sufficient  length  and 
about  1  ft.  deep  may  be  dug  to  contain  the  fire,  over  which  the 
kettles  are  hung  from  supports.    (PI.  59,  Fig.  1.) 

If  fuel  is  scarce,  then  dig  a  trench  as  above  in  the  direction  of 
the  wind,  but  a  little  narrower  than  the  diameter  of  the  kettles  to 
be  used.  Plnoe  the  kettles  over  the  trench  and  fill  in  between 
with  stones,  clay,  etc.,  forming  a  kind  of  flue.  The  draft  may  be 
increased  by  building  a  chimney  of  sods,  stones,  etc.,  on  the  lee- 
ward end  and  enlarging  the  windward  end.    (Fig.  2.) 

If  the  camp  is  to  be  for  a  long  time  and  the  direction  of  the 
wind  liable  to  vary,  a  number  of  such  trenches  mav  be  dug 
radiating  from  a  common  point,  over  which  point  a  chimney  is 
constructed.  Then,  whatever  the  direction  of  the  wind,  the 
trench  opening  in  that  direction  can  be  used,  the  others  being 
closed. 

The  trenches  should  have  a  slight  fall  from  the  chimney  back 
for  drainage,  and  a  means  for  the  water  to  escape.    If  the  ket- 


PLATE  59, 


FIGl 


Ca/mping  Expedients.  215 

ties  are  small  or  of  various  sizes,  rests  of  stones,  scraps  of  iron, 
etc.,  may  be  placed  across  the  trench. 

A  square  hole  may  be  dug  for  the  fire  with  trenches  for  draught 
at  the  corners,  the  kettles  being  placed  on  rests  over  the  fire. 
(Fig.  3.) 

493.— A  grillage  or  kind  of  grate  about  1  ft.  high,  made  of  gas- 
pipe  or  bar-iron,  is  sometimes  used  to  set  over  the  fire,  and  on  this 
are  placed  the  kettles.  (Fig.  4.)  These  are  sometimes  made  with 
movable  joints,  so  as  to  be  closed  for  transportation. 

494. — If  a  covered  kitchen  is  desired,  either  a  trench  similar 
to  Fig.  2  can  be  dug,  or  one  above  ground  can  be  built  with  stones 
and  sods  and  a  tent  placed  over  it,  or  a  cover  constructed. 

495.— To  bake  bread,  when  none  of  the  portable  ovens  of  the 
Commissary  Department  are  carried,  improvised  ovens  must  be 
constructed.  The  simplest  method  is  to  take  a  barrel  with  one 
head  out  (one  with  iron  hoops  best),  lay  it  on  its  side  in  a  hollow 
in  the  ground  and  then  plaster  over  with  wet  clay  6  to  8  in.  thick, 
then  with  a  layer  of  dry  earth  equally  thick,  leaving  an  opening 
of  3  or  4  in.  at  the  top  of  the  closed  end  for  a  flue.  The  staves  are 
then  burned  out  by  a  hot  fire,  which  also  bakes  the  clay  covering, 
forming  an  arched  oven.  To  bake,  after  heating,  the  front  and 
flues  are  closed.  Or  a  pit  may  be  dug  from  6  to  12  in.  deep  and  4 
by  5  ft.  for  the  hearth,  over  this  form  an  arch  with  a  hurdle  or  any 
other  material  available  (Fig.  7),  with  a  chimney  at  one  end  and 
a  door  at  the  other.  Then  plaster  and  cover  the  arch  as  in  the 
barrel  oven  and  bake  the  clay  covering. 

496.— An  oven  may  be  excavated  in  a  clay  bank  (Fig.  6)  and 
used  at  once. 

497.— The  Buzzacott  Army  Field  Oven  (Fig.  8),  which  is  an  ar- 
ticle of  issue,  is  a  complete  camp  cooking  outfit,  consisting  of  oven, 
baking  and  frying  pans,  etc.  All  are  securely  packed  together  and 
can  be  conveniently  carried  in  the  feed  box  of  an  army  wagon  or 
on  a  pack  animal.  To  use  it,  a  bed  of  live  coals  is  first  obtained, 
then  the  oven  after  being  heated  is  placed  on  rests  over  a  bed  of 
coals,  and  a  layer  of  sand  sprinkled  evenly  over  the  bottom  of  the 
oven  to  prevent  burning  out.  In  this  is  placed  the  pans  of  pre- 
pared food  on  suitable  rests  and  the  whole  covered  with  a  hood, 


216  Camping  Expedients. 

On  th,e  hood  is  scattered  a  layer  of  live  coals  and  burning  brands. 
Broiling,  frying,  coffee-making,  etc.,  may  be  done  on  top  of  the 
oven  by  using  the  remaining  pans,  rests,  etc.,  at  the  same  time 
that  the  interior  is  used  for  baking. 

498.— Drainage.  The  camp  beiug  located,  a  system  of  sur- 
face drainage  should  be  carefully  traced  and  constructed.  As 
soon  as  a  tent  is  pitched  it  should  be  surrounded  by  a  shallow 
ditch  outside,  emptying  into  a  company  -ditch.  The  proper  meth- 
od of  doing  this  is  to  have  the  inner  edge  of  the  ditch  come  just 
inside  of  the  skirt  wall  of  the  tent  to  catch  the  water  running 
down  the  side  of  the  tent  and  to  drain  the  interior. 

The  picket  should  be  inside  of  the  ditch.  (Fig.  9.)  To  bank 
earth  up  against  the  tent  soon  rots  the  bottom  of  the  wall. 

499.— Beds.  The  ground  being  generally  too  damp  to  lie  upon 
directly,  all  should  sleep  upon  some  dry  material,  as  straw,  leaves, 
or  preferably  a  low  platform  constructed  of  small  branches  and 
poles,  if  available.    (Fig.  10.) 

If  required  to  sleep  upon  the  ground,  one  will  sleep  more  com- 
fortably if  he  scrapes  out  a  small  hollow  for  his  hips.  Straw, 
hay,  etc.,  for  sleeping  upon  may  be  made  into  mats  with  the  Malay 
Hitch  as  in  Fig.  11. 

500.— Windbreaks.  When  troops  bivouac,  some  protection 
from  wind  may  be  obtained  by  building  up  to  the  windward  a 
pile  of  earth,  sods,  etc.  Where  trees  are  available,  by  resting  a 
pole  on  two  forked  sticks,  4  or  5  ft.  high,  against  which  branches, 
thick  end  up,  are  piled  at  an  angle  of  45**  on  the  windward  side. 
(Fig.  12.)  Hurdles  similarly  placed,  supported  and  covered  (Fig. 
18),  canvas  or  blankets  secured  as  in  Fig.  14,  straw  or  hay  clamped 
between  poles  as  in  Fig.  15,  may  be  used. 

By  throwing  up  either  a  half  or  whole  circle  of  earth  18  ft.  in 
diameter,  from  a  ditch  on  the  outside,  some  protection  may  be 
obtained.  On  the  bank  so  formed  additional  windbreaks  may  be 
placed  or  a  covering  extended  over  it  all  may  be  made.  (PI.  60, 
Figs.  1  and  2.) 

501.— In  cases  of  prolonged  occupation,  if  tents  ar^  not  avail- 
a^ble,  tfifi  trppps  shpyld  builcl  ish^ltei*  pf  some  bJnd, 


PLATE  60. 


218  Cwmping  Expedients. 

Huts  may  be  built  of  timber,  logs,  brushwood,  adobe,  etc.,  in 
connection  with  straw,  bark,  sods  and  similar  materials. 

All  huts  should,  if  possible,  have  their  floors  raised  above  the 
ground  to  allow  free  circulation  of  air  underneath.  (Fig.  3.)  Only 
in  very  dry  soil  and  when  not  to  be  occupied  long  is  it  allowable 
to  sink  them,  if  avoidable.  Space  between  huts  in  the  same  row 
should  equal  the  height  of  walls,  and  passage  in  rear  equal  the 
height  of  ridge.    Hut  sites  should  be  well  pounded. 

Huts  are  ordinarily  constructed  to  contain  a  small  number  of 
men,  but  the  sizes  and  details  of  construction  will  depend  greatly 
upon  the  site  and  materials  available. 

A  very  fair  minimum  allowance  per  man  of  bed  space  is  about 
2.5  ft.  X  7  ft.  with  a  passage  at  foot  from  2  to  4  ft. 

Thus,  the  plan  for  8  men  may  be  taken  at  10  ft.  x  18  ft.,  ar- 
ranged as  in  Fig.  4.  For  12  men,  15  ft.  x  18  ft.  For  16  men,  20 
ft.  X  18  ft.    For  20  men,  25  ft.  x  18  ft. 

For  calculating  the  accommodation  at  the  above  rates,  allow 
1  man  per  pace  of  length  for  a  single  row  of  beds  and  2  men  per 
pace  of  length  for  a  double  row  of  beds. 

502.— Major  Smart,  Medical  Department,  recommends  as  best 
a  modification  of  the  Army  of  the  Potomac  hut,  of  rectangular 
plan  (Fig.  5),  7  ft.  x  13  ft.,  height  to  eaves  6  ft.,  to  ridge  10  ft;  door 
in  middle  of  one  long  side,  chimney  opposite  door  on  outside  of 
wall;  on  each  side  of  doorway  a  double  bunk.  This  hut  to  accom- 
modate 4  men. 

If  logs  are  used,  the  ends  are  trimmed  with  an  ax  where  they 
lap  at  the  corners,  so  they  will  lie  one  upon  the  other  throughout 
their  length. 

503.-— If  made  of  small  timber,  some  style,  as  in  Fig.  6,  with 
thatched  roof,  might  be  used. 

If,  for  any  reason,  it  is  not  desirable  to  build  huts  as  above, 
forms  may  be  used  as  shown  in  Fig.  7,  or  hurdles,  as  in  Fig.  8. 

504.— Sentry  boxes  may  be  made  as  in  Fig.  9,  the  side  cover 
Ing  consisting  of  watling  described  in  Chap.  IX.  and  the  roof 
thatched. 

505.— An  excellent  form  of  bamboo  hut  with  grass  roof,  as 
shown  in  cut,  has  been  successfully  used  In  the  Philippines.    The 


Camping  Expedients. 


219 


corner  posts  were  made  double  for  additional  strength,  the  floor 
being  of  bamboo  strips  lashed  firmly  to  bamboo  floor  beams. 
Wooden  pins  and  rattan  lashings  were  used  throughout.  The  hut 
shown  is  16  ft.  square,  in  the  clear,  and  furnished  comfortable  and 
sanitary  sleeping-room  for  eight  men  on  gold  medal  cots. 


INDEX. 


Par. 

ABATIS,  consists  of,  how 

made 50 

in  shallow  ditch,  of  small 
branches,   in    front    of 

glacis 5 

how  destroyed.^ 41 

ADVANCED  PO^T,  rear  of...    204 
ANCHORS,  number  of,  scarc- 
ity of 343 

substitutes  for 344 

use  of 342 

weights  of,  names  of  parts 

of 341 

aNGLiE,    equal    to   a  given 
angle,  method  of  laying 

out 22 

right,  method    of    laying 

out 18 

re-entrant,  salient,  shoul- 
der       82 

APPROACHES,  in  siege  oper- 
ations   constructed    by 

infantry 154 

AREA,  of  rectangle,  of  trape- 
zoid, of  triangle,  method 

of  finding 25 

ARTILLERY,  in   defense    of 

village,  where  placed...    215 

in  woods 179 

projectiles 9 

to    be   placed   outside   of 

works 87,  151 

AX,  use  of 44 


BALKS,  bay,  etc.,  defined... 284-285 
BALLAST,  for  R.R., object  of    377 
BANK,  GUN,  definition  of, 
relative   advantages  of, 

and  embrasures 70 

dimensions    of,    where 

placed 102 

space  required  for 100 

BARREL,  buoyancy   of,  how 

determined  325 

BARRELS,   closed,    piers   of, 

construction  of 333 

open,   piers  of,   construc- 
tion of 328 

open,  safe  load  of 329 


Par. 
BARRICADE,    use   and   con- 
struction of 61 

for  doors  of  buildings 195 

BATTERIES,  telegraph,  how 

carried 418 

B  AY,  length  of,  how  found ...  317 

BEDS,  camp 499 

BERM,  definition  of,  etc 65,  99 

advantages  and  disadvan- 
tages of 78 

RINDING,  fascines 117 

BISECTING  an  angle,  method 

of 20 

BLOCKS,  description  of,  etc., 

running 228 

BLOCKHOUSE,  use  and  con- 
struction of 144 

Spanish 145a 

in  isolated  places 145 

BOAT,     buoyaiicy     of,     how 

found 316 

BOX  or  barrel  to  sling 223 

ponton,  construction  of . . .  323 

BRACKETS,  .telegraph 410 

BREAKING  loads  of  ropes  . . .  218 
BREAKS  in  telegraph  lines  .  419 
BRIDGE,   anchored  to    haw- 
ser   343 

beams,   of    iron,  how    de- 
stroyed    446 

connection  of  with  shore, 

how  made 350 

computing  strength  of..  .  255 

double  lock 27^ 

expedients 278 

floating,     description     of, 

modi  ttcation  of  306 

floating,  improvised 352a 

flying,  description  of 3u9 

forming,  by    sue  cessive 

pontons 346 

forming,  by  parts 347 

forming,  by  rafts 348 

forming,  by  conversion  . .  349 
masonry,  how  destroyed. . 

.....440-441 

maxi  num  load  for 247 

namf  of,  how  derived. .  .248,  310 

Paine's 260 

pile 269 


222 


hidex. 


Par. 


BRIDGE— Continued. 

protection  of,  from  float- 
ing objects 352 

railroad,  repair  of 407 

requirements  of  244 

short,  how  anchored 343 

single  lock 274 

single  sling 276 

spar  railroad 245 

suspension 280-6 

suspension, how  destroyed    450 

swing 351 

trail  308 

treble  sling  277 

twenty-five  feet  or  le«»}a.. .  .258-9 
twenty-five  feet  or  over  . 

261,271,276 

BROADSIDE  VILLAGE,  how 

defended 1V\ 

BliUSH  huts 503 

sentry  boxes 504 

BRUSHWOOD,  bundles  of,  va- 
rieties and  sizes 115 

rate  and  method  of   clear- 
ing        40 

roads. 371 

BUILDING,  defense  of,  how 
regarded,  first  line,  how 

far  distant  191 

doors  of,  how  barricaded,    195 

flank  defense  of  199 

how  used  for  defense 189 

loopholingof 194 

materials  used  in  defense 

of 200 

precautions  in  defense  of.    19^ 

removal  of 48,  438 

requisite  of,  for  defense    .    190 
steps  in  preparing  for  de- 
fense      193 

windows  of,    how    barri- 
caded      197 

BUOYANCY  of  casks,  how  de- 
termined      325 

BUZZACOTT   oven,    descrip- 
tion of 497 

CABLE,  charge  Of  explosive 

to  cut 450 

swinging,  length  of 309 

CAMP  BEDS  499 

CAMPS,  drainage 498 

dry   and   healthy    sites 

for 457,459 

selection  of 455,  45«,  462 

unhealthy  sites  for 458,  460 

windbreaks  for 600 

C  AN  IS  TE  R.  description  of. . .      11 

CANVAS  PONTON,  U.  S 319 

CANVAS  RAFT,  description  of  303 
CAPITAL  of  field  works  ...  82 
CAPONIERS,  objections  to,  85,  146 

stockade  work  used  for 188 

used  in  flanking  buildings,    199 

CAPSTAN,  description  of 241 

improvised  field 243 


Par. 
CASEMATES.use  and  general 

form  of 138 

how     constructed,    floor 

space  in 139 

CENTRIFUGAL     FORCE    of 

train 383 

CHARCOAL,  uses  of 481 

how  made ^. . .    482 

CHARjGES,  several  exploded 

at  same  time 439 

CHESS  described 248 

CHEVAUX-DE-FRISE 56 

CHOKER  FASCINE,    descrip- 
tion and  use  of 117 

CIRCULAR    VILLAGE,    how 

defended 214 

CLARIFICATION  of  water  . .     476 

CLAY  ROADS  367 

COMMAND  OF  WORKS,  defi- 
nition of 71 

COMMON  T  KENCH  work,how 

made,  uyesof 156 

COMMUNICATIONS,      c  o  n  - 

struction  of 373,374 

i n  woods 177 

CONCENTRATED    LOAD  on 

bridge 253 

CONDUCTOR,     metallic,    for 

telegraph 408 

CONNECTING    WIRES,    how 

done 431 

CORDUROY  ROADS 370 

COUNTER-SCARP,  definition, 

etc.... 65,  79 

galleries 85 

COVERforguns 40a 

in  woods,  how  obtained .. .    176 

CRAB 240 

CREST,  exterior 67 

interior 66 

military 153 

CRIB  piers,  construction  of..     268 
ponton,  construction  of...    322 

CROSS,  in  telegrjiph  wires 419 

CROSS  ARMS,  telegraph 410 

CROSSING  of   rivers,     selec- 
tion of,  how  determined,    289 

CROSSINGS,  railroad 385 

CROW'SFEET 56 

CUTTING,  how  defended. .  .171, 172 


DE  '  O  LOAD  on  bridges 253 

DEBRIS,  removal  of 48 

DEFENDERS  of  woods,  num- 
ber of 179 

DEFENSE,  of  fences 368 

passive,   with    respect   to 

lines  of  works 149 

DEFILADE,  definition  of....  88 

In  plan 89 

in  section 90,  91 

with  two  planes 92 

DEPTH  of  fords 290 

DERRICK,  description  of . . . .  237 

in  using 240 


Index. 


223  r 


Par. 
DESTROYING    railroads,    by 

whom  done 399.400 

by  whom  ordered 401 

of  telegrraph  lines 420 

DETONATOH 429 

withfuse 428 

electrical 429 

DIGGING  wells 470,  471,  472 

DIMENSIONS  of  loopholes  ...    164 

DISABLING  railroads 398 

DISTANCE  between  two  in- 
accessible points.method 

offlndinpT 24 

D!8TRIBUTED  load 253 

DITCH 65,81,361 

depthof 96 

method  of  digging 1"1 

DOORS,  how  barricaded 195 

DOUBLE  lock  bridge 275 

DRAINS,  catch  and  covered. .    3fil 

DRAINAGE  of  camps 498 

of  roads 361 

DRINKING  water 465-9 

DRIVEN  wells 473-4 

DRIVING  piles 270 

DYNAMITE,  use  of  with  de- 
tonator        428 


EARTH,  excess  of  at  salients.  97 
in    embankments,     space 

occupied  by 96 

roads 366 

EARTHWORKS,     calculation 

of  dimension  j!  of 95 

ELECTRICAL  fuse 429 

EMBANKMENT,  how  defend- 
ed   170 

EMBARKATION,  in  ferrying  301 

EMBRASURE 69 

used   when,    details     and 

construction  of. 103 

space  required  for 100 

ENGINE,  locomotive 389 

ENGINEERING,     Military, 

Field,  definition  of 1 

EPAULEMENT,  gun 4()a,  70 

relative  advantage  of,  and 

embrasures 70 

EQUILATERAL  TRIANGLE, 

method  of  laying  out —  21 

ESCAPE  in  telegraph  lines...  419 

ESCARP 65,  79 

EXPEDIENTS,  bridge 278 

EXPLODER,  electrical 430 

EXPLOSIVES,  kind  general- 

ly  used 421 

table       of      comparative 

strength  of 453 

EXTENDING  along  zig-zag..  155 

workinsr  party 109, 110, 155 

EXTfc:NSION   on   flying    sap, 

method  of 158 

EYE-BARS,  how  cut 448 

j;yE-SPLICE,  to  make 222 


FACES  of  works 82 

FARMS,  principles  of  defense  , 

applied  to 203  » 

FASCINES,  size,  weight,  and  f' 

making  of 117 

FASTENINGS,  rail 382 

FAULTS  in  telegraph  lines.419-20 

FENCES,  defense  of * 168 

removal  of  when 48 

FERRY,  the  rope 307 

FERRYING  by  boat,  embark- 
ation, and  unloading 301 

by  raft 302 

FIELD  GUNS,  destruction  of  451 

range  of 13 

FIELD  LEVEL,description  of  26 

FILTERS,  portable 483-4 

simple 485 

FILTERING  water 480-1 

FIRE,  as  regards  direction, 

trajectory 8 

double  tier  of,  for  walls...  167 

sector  of,  discussion  of —  86 
working  parties  exposed 

to Ill 

FLANK  defense  of  buildings  199 

FLANKS  of  works 82 

FLOOR  space  in  casemates. . .  139 
FLOATING  piers,  essentials 

of 314 

FLYING  BRIDGES,  raft  for. .  340 

telegraph  lines 418 

sap,  description  of 157 

sap.  method  of  extension 

along 158 

FORDS,  how  made   impassa- 
ble   58 

with  sandy  bottom 291 

depth  of,  requisite  of 290 

in  mountainous  country. .  291 

level  country 291 

how  marked,  position  of, 

how  determined 293 

precautions  in  selecting. .  295 

re-examinations  of 296 

where  found 292 

FOREGROUND,     extent     of 

clearing 43 

FORM,  strap  iron  gabion .....  120 

wicker  gabion 118 

of  roads 359 

FORMING  BRIDGE   by  con- 

version 349 

by  parts 347 

by  rafts 348 

by  successive  pontons   ...  346 

FORTS,  how  distinguished. . .  84 
FORT     WaGNER,    parallels 

and  approaches  to 160 

FORTIFICATION,  classes  of.  2 
compared  to  other  milita- 
ry expedients 7 

oblect  of 

subdivision  of  field 3 

FOUGASSE.conBtruotlon.use 

anachavgefor,,,,. „  \^ 


224 


Index. 


Par. 

F RAISES,    construction   and 

use  of 55 

FROGS 384 

railroad,  how  destroyed. .  444 

FUSE 427 

how  used 428 


GABIONS,  hoop  or  strap  iron, 

weififht  and  making  of...  120 

method  of  carrying 157 

sheet  iron,  making  of 121 

wicker,  size,  weight,  and 

making  of 118 

making  of  without  a  gabi- 
on form 119 

GATES,  destruction  of 437 

GIN,  description  of 239 

using 240 

lashing,  making  of. 227 

GLACIS. 65.80 

GORGE  of  works 82 

GRADIENT, limitingof  roads  355 

GRAIN,  removal  of  standing.  47 

GRASS,  removal  of  standing.  47 

GRAVEL  ROADS 368 

GRILLAGE 493 

GAUGE  of  railroads 380 

GUARDING  water  supply     .  464 

GUN-COTTON 422 

how  detonated 428 

GUN     EPAULEMENTS    nnd 

pits 40a 

GUNPOWDER,  how  ignited.  428 

used  as  an  explosive 424 

GUTTERS 361 


HARD  WATER  477 
HASTY     DEMOLITION,     ta- 
bles    showing     charges 

for 452 

HEAD  LOGS,  use  of 40 

HEALTHY  CAM  PS 4n7.  459 

HEDGES,  advantages  of.  how 

derived,  principles  of...  169 

removed ,  when 48 

HEIGHTS    over    which    fire 

mav  be  delivered  13 

HITCHES,  knots,  etc 219 

HOLDFASTS,  description  of. .  243 
HOOPS,  making  of,  for  strap 

iron  gabions 120 

HORSE,  power  of  on  grsades..  356 

HOUSES,  demolition  of 438 

HURDLES,  continuous,  con- 

sti'ucl  ion  of 123 

size,weight  and  making  of  122 

HUTS,  brush. 503 

how  made,  etc 501 

Army  of  Potomac  (Major 

Smart's) 502 

allowance  of  space  in ftOl 

bamboo 605 


of,     how     in- 


Par. 

297 


ICE 

thickness 

CI  eased 299 

thickness   of  for  various 

loads 298 

INFANTRY      APPROACHES 

in  siege  operations 154 

INTERVALS  between  trench- 
es    36 

method  of  taking.by  work- 
ing parties 100 

usual     for    working   par- 
ties  Ill,  112 

INSU  L ATORS,  telegraph 412 

INSULATED  WIRE  JOINTS  431 
INTRENCHMENTS,    HASTY, 
advantages   and    disad- 
vantages of 39 

concealment  of 38 

conditions  to  be  fulfilled 

by '28 

consist  of 28 

for  men  standing 31 

for  skirmishers  lying 28 

for  two  ranks  kneeling...  30 

for  supports  and  reserves.  33 

intervals  in  line  of 36 

iFolated- 32 

location  of  depends  upon.  35 

on  slopes 34 

Spanf  sh 31 

IRON  PLATES,  how  cut 445 

ISOLATED  PITS b2 


JOINTS  for  telegraph  wire. . .  417 

American  twist 417 

insulation  of 431 

rail 381 

JUNCTIONS,  railroad 386, 


KING-POST  TRUSS 272: 

KITCHENS 491-2* 

covered 494J 

KNOTS,  hitches,  etc 219» 


LANCES,  military,  telegraph.  418 

LASHINGS,  gin 227 

rack 224 

shear 226, 

transom 225 

L  ATRINES 487,  490, 

LEAKS  in  telegraph  line 419 

LEVEL,  field,  description  of.  26 

uses  of 27 

LINES,  cutting  of  ditch  and 

trench,. 101 

LINE,  first,  falling  back  past 

housea. ,,,  192 

par  all  ell   to     given    line, 

metliod  of  constructing.  23 
LINES,  fvecond  and  thiiBd  in 

woc^S. 16&- 


.  In 


Index, 

Par. 


225 


iLOADy  distributed  ,dead,  and 

moving 253 

LOADING    HORSES    in  rail- 

TOad'cats 393,  394 

LOADING  WAGONS  on  rail- 
road cars : 3Q6 

LOG,  cubic  contents  of 254,335 

buoj'^a  ncy  of. . . . : ...;..,.    3:^4 

ILOGS,  pi  rs  of,  construction 

of   : 3H8^ 

LONG  SPLICE,  to  make 221 

LOOPHOLES,  atmensions  of    164 
height  of,  how  influenced.    166 

how  made 40 

in  buildings 194 

LOO PHOLING  WALLS 163 

method  of 164,165 


MACADAM  ROADS 364 

MACHICOULIS  gallery,  con- 
struction of,  use  of 199 

MAGAZINE,     general      plan 

of 141,  142 

large,  small  in  parapet 140 

of  gabions  and  fascines. . .    143 
rifle,    range,    speed,   and 

flreof 14 

MAGNETO  EXPLODE^ 430 

MARKING  FORDS 293 

MATEKIALS  for  bridges 287 

.  for  road  coverings 365 

revetting 114 

used  in  defense  of  build- 
ings      200 

MAXIMUM  LOAD  for  bridge 

MERLON,  deflnition  of,  rule 

as  to  adnimum  length  of 

METAL  TIES 37 

MILITARY  ENGINEERS, du- 
ties of 421 

MILITARY        TELEGRAPH 

lines 418 

MINES,  land,  quantity  of  ex- 
plosive necessary 60 

MOVING  or  LIVE  LOADS.    ..     253 


104 


OBJECTS,  floating,  protec- 
tion of  bridge  from  352 

OBSTACLES,  conditions  gov- 
erning use  of 49 

OFFICE  TELEGRAPH.tveat- 

ment  of  when  captured.    420 

OVENS 495-6 

Buzzacott 497 

ORGANIZATIONS,  or  parts 
of,  used  as  working  par- 
ties       42 

OVERHAUL  TACKLE 231 


PAINE'S  BRIDGE 260 

PALISADES,  consist  of 54 

PALISADING,  destruction  of  435 

PAIRING 118 


Pm. 

PAN  COUPE 101 

PARADOS,  deflnition  of 

meihod    of     determining 

\    height  of 93 

PARALLEL  to  a  given  line, 

.   method  of  constructing.      23 
PARALLELS  and  approaches, 

,  Fort  Wagner 160 

PARAPET 63,  67,81 

PERPENDICULAR  to  a  line 

method  of  erecting 19' 

PICKETS,  forked 119 

gabion 118 

PIERS,     bridge,      how      de- 
stroyed   440,  449 

floating,  essentials  of 314 

of  casks,    precautions   in 

using 327 

of  open  boats,  precautions 

in  using 315 

of  open  caskn,  construc- 
tion of 328 

of  closed  casks,  construe 

tlonof 330,333 

of  logs,  construction  of  .338,  339 

PILEBRIDGES 269 

driving 2'70 

PLANK  ROADS 372 

PLANKS,  when  used  for  re- 
vetments      124 

PLOWS,  useof 33 

PONTON  CANVA>,  U.  S.. 
crib,  construction  of. 
PONT(>N,  box,    construction 

of 

reserve  train,  U.  S 

wagon  body,  construction 

of 

POLES,  telegraph,  how  num- 
bered     415 

telegraph,  how  guyed, 
number  tomile,prepaia- 
tion  of,  protection  from 
lightning,      raising     of, 

size  of,  where  run 409,  411 

PORTABLE  RAMP 393 

fllters  483,  484 

truss  279 

POSITION .'  defensive,"  deflnjl 
tion  of,   chief   requisite 

of 4 

choice  of 42 

strength  of 153 

conditions  to  be  fulfllled..       4 

of  ford,  how  determined. .    293 

POWER  of  horse  on  slopes. .   .    356 

exerted  by  man 236 

of  tackle 233-5 

PRECAUTIONS,    additional, 

in  defending  buildings..    198 

in  fording 295 

PROFILES,  angle,  how  deter- 
mined        94 

deflnition  and  nomencla- 
ture of 65 

normal,  of  fleld  works 99 


319 
322 


323 

320 


324 


226 


Index, 


Par. 

PROFILING,  method  of 94 

PU  LLE  Y,  descriptiou  of 228 

QUEEN-POST  TRUSS 273 

RACK,     fascine,  description 

and  use  of 117 

lashing  to  make  224 

RAFT,  canvas,  description  of,  303 

for  trail  bridge ;W8 

of  skins 304 

RAFTS,  advantages  and  dis 

ad  vantages  of :^5 

for  flying  bridge 340 

swinging,  for  traffic 351 

RAIL  Fastenings :«2 

form  of 380 

joints 381 

how  cut 435 

straightening 407 

RAILROAD,  bridge 245 

crossings :^85 

junction 386 

wye 387 

turntable 388 

RAILROADS,  duties  of  troops 

in  connection  with 375 

descri  ption  of 377 

destroying  and  disabling, 

by  whom  done 398-400 

how    disabled    and    des- 
troyed   402,  403 

repair  of 404 

rolling    stock,   buildings, 
etc 390,  391 

RAM  P.  port  a  Die 393 

Major  Fechet's 397 

semi-permanent 395 

simple  form  of 392 

RANDING 1*22 

REDOUBTS 84 

RELIEFS,  1st,  2nd  and  3rd  of 
working  party,   cutting 

lines  for  tasks  of 

of  field  work,  definition  of 

RESERVE     TRAIN,    ponton, 

U.  S 320 

REVETMENT,    definition   of  113 
making   and    qualities  of 

adobe 137 

of  brushwood 128 

of  fascines  129 

of  gabion 130 

of  hurdle  and  continuous 

hurdle 131 

of  pisa 136 

of  plank 124,  132 

of  posts 135 

of  sand  bag 133 

of  sod 126,  133 

of  timber 125,  132 

of  bamboo 137a 

RIBBANDS 55 

ROAD-BED 360 

defense  of 173 

materials 365 


101 


Par, 

ROADS,  brushwood 371 

clay 367 

corduroy 370 

desirable  conditions  in 354 

drainage  of 361 

earih 366 

form  of 359 

gravel 368 

knowledge  of 353 

limiting  gradients  of 355 

plank 372 

repair  of 369 

surface  of 362 

width  of 358 

ROADWAY,  weight  of,  steadi- 
ness of 313 

width  of  on  bridges. .  .248,  280-6 
ROPE,     breaking     loads    of, 

weight  of 218 

composition,  size  of,  etc  . .  216 

ROPE,  parts  of 219,  230 

rule  for  strength  of 217 

expedient  for  tightening,  308 

ROUND  TIMBER,  strength  of,  255 

RUNNING  BLOCKS 228 


SAG  in  telegraph  wire 414 

SALIENT  village,  liow  de- 
fended   212 

SAND-BAGS,  materials,   size, 

capacity,  and  filling 127 

SAP,  flying,   description  of..  15V 

SAW,  teeth  of 44 

use  of 44 

SECTOR  OF  FIRE,  definition 
of  and  application  to  dif- 
ferent traces 86 

SELECTING  CAMPS 455-6,  462 

SENTRY  BOXES 504 

SEWING,  liiethod  of ,  for  gabi- 
ons and  hurdles 18 

SHE  \R  LASHINGS 226 

S  HE  A KS,  description  of 238 

method  of  using 240 

SHKLL 9 

charges,  how  exploded 12 

penetration 15a 

shrapnel 10 

SHORT  SPLICE,  to  make 220 

SHOVEL  ERS,  extra,  provid- 
ed when 101 

SIDINGS,  railroad 384 

SINGLE  LOCK  BRIDGE. 274 

SINGLE  SLING  BRIDGE 276 

SITE  for  floating  bri  dge,  selec- 
tion of 311 

plane  of,  definition 73 

SIZE  OF    TELEGRAPH 

WIRE 408 

SLEWING 122 

SLOPE,  banquette 65 

description  of 17 

exterior 65,  77 

interior 65,  75 

superior 65,  76 


Index. 


227 


Par. 

SMALL  PITS,  how  made 57 

how  destroyed. 453 

SNATCH  BLOCK 228 

SODS  for  revetments,  cutting 

and  laying 126 

SPAN,  superstructure,  string- 
ers oi-  balks,  side  rails, 

etc 248 

SPANS,  25-ft.  or  less 258  259 

25-ft.  or  over 261.  271,  276 

SPARS,  arrangement  of 257 

SPLICE,  long 221 

eye 222 

SPLINTEll  PKOOF  for  Iren- 

STOCKADE,    advantages    of, 

definition  of 180 

how  destroyed 436 

kind  of  timber  preferable 

for 186 

loopholes  in 184 

loopholes,  when  cut  in 185 

of  vertical  timbers 182 

of  same,  square  and  round 

timbers 183 

of  horizontal  timber 187 

STOCKADE,  of  K.  R.  iron,  de- 
stroyed how 436 

when  employed 181 

work   used   for   tambours 

and  caponiers 188 

STRAIGHTENING  KAILS..    .  407 
STREAMS,   unfordable,    how 

passed 294 

velocity    of,   how    deter- 
mined    296 

width  of,  how  determined,  312 

STRENGTH  OF  MATERIALS  249 

of  rope 217,  218 

SUB-DRAINS 361 

SUSPENSION  BRIDGES 280-6 

S  WITCH,  split  and  stub 384 

TAB  LE  of  breaking  loads  ...  218 

of  constant  "C" 253 

of  weights  of  materials 256 

showing  amounts  of  revet- 
ting   materials    for    100 

linear  feet  of  revetment,  137 

TACKLE,  description  of 229 

formula  for  power  of 235 

powerof 233-4 

to  prevent  twisting 232 

to  round  in,  to  overhaul. . .  231 

TAMBOUR 147 

stockade  work  used  for. . .  188 

used  in  flanking  buildiufs,  199 

TASKS (PI.  14,  16)  111,  112 

laying  out  of 101 

in    constructing  parallels 

and  approaches PI.  22 

responsibility  for  comple- 
tion of 106 

TELEGRAPH  MESSAGES.   ..  408 

lines,  how  destroyed 4'20 

TELEPHONE,outpost  cart  for  418 


Par. 

TELFORD  ROADS 363 

TERREPLEIN 74 

THICKNESS    of   materials 

proof  against  small  arms,  15 

TIES,  metal 379 

wood 378 

TIMBER     BRIDGE,  how  de 

stroyed     433 

felled,  removal  of 45 

kinds  preferable  for  stock- 
ade   186 

rouu'l  for  revetments 125 

standing,  removal  of 43,  44 

TOOLS,  carrying  of  by  work- 
ing parties 108 

cutting,  intrenching  used 

in  the  field 41 

taking  of,  by  working  par- 
ties    107 

used  in  felling  tember 44 

TORPEDO,  U.  S.  bridge 433 

TORPEDOES,  automatic 453 

TRACE,  definition  of 64 

selection  of 89 

TUANSOM,  strength  of 250 

TllAVEKSE,  definition  of 68 

method    of     determining 

height  of ^3 

TREAD  BANQUETTE 65 

TREBLE  SLING  BRIDGE....  277 

TREE  INSULATOR  and  tie..  415 

TKKES,  cutting  of 44,45 

how  to  fell  with  explosives,  432 

TRKNCH 65 

common.nsesof.howmttde,  156 

d  rainage  of 98 

method  of  digging lUl 

TRENCHES,  advantages  and 

disadvantages  of 39 

conditions  to  be  fulfilled 

by 28 

disguising  location  of 38 

intervals  in  line  of 36 

kneeling  or  sitting 30 

location  of 35 

lying 29 

standing 81 

Spanish  31 

TROOPS,  weight  of  on  bridge,  252 

TRESTLES,  capped 264 

tie  block 263 

two-legged 265 

three-legged 266 

four-legged 267 

six-legged 262 

TRUSS,  king- post 272 

queen-post 273 

portable 279 

TUNNELS,  how  destroyed....  442 

repair  of 406 

TURNTABLES,  railroad 388 

UNLOADING  in  ferrying....  301 

horses  from  R.  R.  cars.. 393,  394 

wagons  from  cars 396 

URINALS 488,  489 


228  Index. 

Par. 
VELOCITY  of  streams,  how  i 

determined 296   i 

VILLAGE,  advantages  and 
disadvantages  of  for  de- 
fense      206 

artillery,  wliere  placed  in 

defense  of. 215 

broadside,  how  defended..    213 
circular,  how  defended....    214 
cover  for  supports  and  re- 
serves in 215 

in  defense  of,  precautions 

necessary 205 

defense  of  depends  on..  ..    208 
arrangements  for  defense 

of 205 

garrison    of,    how    deter- 
mined     211 

objfcts  in  holding 207 

salient,  how  defended 212 

value  of,  for  defense 205 

arrangement  for  defense 
of,  how  made 210 


WAGON  BODY  PONTON,  con- 
struction of 324 

WAGONS,  prepared  for  cross- 
ing on  ice 299 

WALLS,  for  double  tiers  of 

fire 16T 

discussion  of  as  military 

expedients 161 

loopholing 163-5 

preparation  of  for  defense    162 

removal  of 48 

how  destroyed 439 

WATER,  clarification  of 476 

drinking 465-9 

filtering 480-1 

guarding 464 

necessity  of  and  amount 

required 463-4 

WATER  TABLES  on  roads...    361 

WATLING 118 

WEEDS,  removal  of 47 

WEIGHT  of  materials 256 

of  rope 218 

of  troops  on  bridge 252 

WELLS,  digging  of 470-2 

driven 47;^4 

WIDTH  OF   ROADS 358 

WINCH 240 

WINDLASS,  description  of..  241 
WINDBREAKS,  for  (tamps....  500 
WINDOWS  of  buildings,  how 

barricaded 197 


Par. 

WIRR,  connection  of 431 

entanglements,  high,  low, 

how  made 52,  53 

entanglements,  how  de- 
stroyed     464 

how    stretched,    hanging 

of ,  secured  to 414 

liow  strung  across  roads.. .    411 
how  strung  across  streams    415 

telegraph 408 

tie 413 

WITHES,  making  and  use  of     117 

WO()D<,  artillery  in 179 

communications  in 177 

cover  in 176 

lying  beyond  position 175 

number  of  defenders  of...    179 

preparation  of  edge  of 174 

2d  and  3d  lines  in 178 

WORKS,   constructed   by 

troops  to  occupy 5 

double  line  of 150 

fixed  types  of  necessary. . .       t> 
groups    of,   intermediate, 

when  used 149 

line  of 148 

advantages  and  principles 

of 149 

WORKS,  field,  conditions  to 

be  fulfilled 62 

calculation  of  cross  sec- 
tion of 95 

classification  as  to  trace. .      83 

defilade  of 88,  89  90,  91,  92 

details  of  constiniction  of 

99,  100,  101 

length  of  crest  for  as- 
sumed garrison 100 

open,  closed,  and  half 
closed,  definitions,  ad- 
vantages, and  disadvan- 
tages       83 

continuous  line  of,  crem- 
aillere,  blunted  redan, 
redan  with  curtains,  te- 
naille.  tenaille  and  re- 
dan, trace  of 152 

WORKING  parties,  extensio»» 

of 109.  110 

organization  of 105 

whenunderfire Ill 

WYE,  R.  R 387 

ZIG-ZAG,  direction  of,  length 

of 159 

extending  along 155 


YB  49784 


/f62 


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